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ANSWERS
FOR THE REVIEW/TUTORIAL
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| 1. |
Answer |
5 |
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Evaluate –
x2 – 3x + 9 for x = 1 |
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When substituting
x = 1 in – x2 |
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be sure to do the exponent before the multiplication by
– 1 |
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to get –
(1)2 = – 1. So –
1– 3 + 9 = 5 |
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| 2. |
Answer |
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| When multiplying
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so that
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| 3. |
Answer |
2(3x -
y) |
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Using the distribute
law -2(y - x) = -2y + 2x we get: |
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5x– 2(y
– x) – x |
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= 5x–
2y + 2x– x |
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= 6x
-2y |
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= 2(3x
- y) |
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| 4. |
Answer |
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| To divide
by 3, we invert and multiply |
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| 5. |
Answer |
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Write the numerator
as a single fraction with denominator of 4, |
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and write the denominator
as a single fraction with denominator of 6, |
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divide |
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by |
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Be sure to invert
and multiply to get |
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Here we divided
the denominator 4 and the numerator 6 by 2. |
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| 6. |
Answer |
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| since
x4 is positive. Similarly |
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| 7. |
Answer |
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| Since |
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we write |
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| 8. |
Answer |
–24x5y8
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When
multiplying exponent expressions with the same base, keep the |
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base and add
the exponents thus, x3(x2) = x5
and y(y7) = y8 |
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| 9. |
Answer |
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Write the equation
of the line in the form y = mx + b or where m
is the slope. |
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3y =
2x – 10 |
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| 10. |
Answer |
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| Write |
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are adding |
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| 11. |
Answer |
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Multiply both
sides of the equation by the denominator x – 3 |
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| Use the
fact that |
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1 – 3(x – 3) = x |
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1 – 3x + 9 = x |
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10 = 4x |
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| 12. |
Answer |
x = – 5, x = 5 |
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There are two
values of x whose absolute value is 5 |
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|-5| = 5 and
|5| = 5 |
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| 13. |
Answer |
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We factor x2
– 3x = x(x– 3) and 9 – x2
= (3 – x)(3 + x) |
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Remember the
difference of squares factorization
a2 – b2 = (a – b)(a
+ b). |
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Thus we get |
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Use the fact
that x – 3 = – (3 – x), so
that |
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Putting this
together we get |
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| 14. |
Answer |
x
< – 6 |
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2x + 1
> 3x + 7 |
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Subtract 3x
from both sides – x + 1 > 7 |
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Subtract 1 from
both sides – x > 6 |
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Multiply by –
1, we get x < – 6 |
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Remember multiplying
an inequality by a minus changes the sense of the arrow. |
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| 15. |
Answer |
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and |
x
= – 2 |
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Consider
the standard quadratic equation ax2 + bx + c
= 0, |
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| whose solution
is |
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For
the solution of 2x2 + 3x – 2 = 0, a
= 2, b = 3, and c = – 2. |
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Since
the discriminant b2 – 4ac = 32 –
4(2)( –2) = 9 + 16 = 25 is a |
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perfect
square, we can factor directly: 2x2 + 3x – 2
= 0, |
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(2x
– 1)(x + 2) = 0 |
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x =
– 2 |
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| 16. |
Answer |
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For the solution
of 2x2 – 3x – 4 = 0, we have a = 2, b
= – 3, c = – 4. |
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The discriminant
b2 – 4ac = (– 3)2 – 4(2)( – 4) = 9
+ 32 = 41 is not a |
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perfect square
so that we must use the quadratic formula and get |
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| two real
roots: |
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Thus |
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| 17. |
Answer |
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For the solution
of 2x2 – 6x + 5 = 0, a = 2, b =
– 6, c = 5 |
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The discriminant
b2 – 4ac = (– 6)2 – 4(2)( 5) = 36
– 40 = – 4. |
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Since the discriminant
is negative, the two roots are imaginary. |
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| Thus, here
we use |
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We can reduce
the answer by factoring 2 in the numerator |
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| 18. |
Answer |
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The negative
exponent means we have to take the reciprocal of what is in |
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| the parentheses
and then square. |
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Remember when
raising a fraction to a power, both the denominator and |
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numerator are
raised to that power |
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| 19. |
Answer |
x = 3,
y = 2 Solve for x and y there are two methods
that are often used. |
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Addition method:
Multiply the second equation by – 5 |
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5x – 3y
= 21 |
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– 5x –
25y = 35 |
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Add the equations
to get: |
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– 28y =
56 |
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Substitute back
into the second equation to get: |
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x + 5(–
2) = – 7 |
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x – 10
= – 7 |
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x = –7
+ 10 = 3 |
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Thus x =
3, y = 2. |
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Substitution
method: Solve for x in the second equation to get: |
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x = –7
– 5y |
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Substitute for
x in the first equation to get: |
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5(–7
– 5y) – 3y = 21 |
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–35
– 25y – 3y = 21 |
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–35
– 28y = 21 |
| Add 35 |
–
28y = 21 + 35 |
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–
28y = 56 |
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Divide
by – 28 |
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Substitute in
equation two to get x. Substitute the value y = – 2 |
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in x =
– 7– 5y to get x = –7– 5(–2) = – 7 + 10 = 3 |
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Thus x =
3, y = 2. |
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| 20. |
Answer |
Answer: 3 <
x < 7 |
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We can do the
problem algebraically or geometrically. |
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Algebraically: |
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|x - 2| < 5 means –5 < x– 2 < 5 |
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So by adding
to 2 all three parts of the inequality we get |
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–5 < x
–2 < 5 |
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–5 + 2 < x
–2 + 2 < 5 + 2 |
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–3 < x
< 7 |
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Geometrically: |
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|x - 2| <
5 means that the distance (in both directions) from x to 2 is less
than 5. |
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So
if we move 5 units to the right (up the axis) from 2 we get 7 and 5 units |
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to the left (down
the axis) from 2 we get –3 |
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| 21. |
Answer |
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| The least
common denominator is xy. Thus |
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Since the denominators
of the two fractions are now the same, |
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we can add the
numerators getting |
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| 22. |
Answer |
(x – 3)(x
+3)(x2 + 9) |
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Recall
the factorization of the difference of squares a2
– b2 = (a – b)(a + b) |
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x4
– 81 is a difference of squares namely (x2 )2
and 92. |
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x4
– 81 = (x2 – 9)( x2 + 9). The first
factor is again a difference of squares: |
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(x2
– 9) = (x – 3)(x +3) |
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x4
– 81 = (x2 – 9)( x2 + 9) = (x
– 3)(x +3)(x2 + 9) |
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x2
+ 9, the sum of squares, does not factor |
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| 23. |
Answer |
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The least common
denominator is 24y. |
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| Thus |
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Here since the
denominators are the same we add the numerator. |
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| 24. |
Answer |
The lines are
parallel. |
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If you solve
for y in each equation to get the form y = mx + b,
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you can examine
the slopes m and the y intercepts b. |
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1 becomes: |
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2 becomes: |
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which reduces
to |
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Since the slopes
are equal and the y intercepts are not, the lines are |
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parallel. In
the case that both the slopes and the y intercepts were equal, |
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the lines would
be the same. |
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In the case that the slopes
are unequal, the lines intersect in one point. |
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| 25. |
Answer |
2 |
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| Think of
as |
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as |
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is the
cube root of 8 often written as |
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| So that |
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the meaning
of a negative exponent. |
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is the
square root of 4 |
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written |
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Thus |
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| 26. |
Answer |
x <
2 or x > 3 |
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x2–
5x + 6 > 0 |
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To find the solution
set for x set the inequality equal to zero and factor and solve
for x: |
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x2–
5x + 6 = 0 |
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(x – 3)(x
– 2) = 0 |
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x = 3,
x = 2 |
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Since the inequality
is strictly greater than zero, neither of these are in the solution set.
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These two numbers
divide the x axis into three sections: |
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| – ¥
< x < 2,
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2 < x <
3, |
and 3 < x
< ¥ |
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Pick any "test"
number for each section and substitute into the inequality: |
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For – ¥
< x < 2, say x
= 0. |
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Substituting
x = 0 into x2– 5x + 6 gives us (0)2
– 5(0) + 6 = 6 |
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which is greater
than zero. |
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Thus – ¥
< x < 2 is part
of the solution set. |
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| For 2 <
x < 3, we can test with |
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or |
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into x2–
5x + 6 gives us |
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which
is less than zero. |
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Thus 2 < x
< 3, is NOT in our solution set. |
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For 3 < x
< ¥,
we can substitute x = 4 to get |
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42
– 5(4) +6 = 16 – 20 + 6 = 12 > 0. |
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Thus 3 < x
< ¥ is
part of the solution set. |
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Thus the complete
solution set is {x| – ¥
< x < 2 or
3 < x < ¥}
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which can also
be written in interval notation as (– ¥,
2)
(3, ¥). |
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| 27. |
Answer |
28 |
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If f(x)
= x3 + 1, f(3) = 33 + 1 = 28 |
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| 28. |
Answer |
The horizontal
line one unit above the x axis. |
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| 29. |
Answer |
The vertical
line 3 units to the left of the y axis. |
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| 30. |
Answer |
The graph of
2x + 3y = 2 is |
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To graph 2x
+ 3y = 2, we need to find any two points which lie on the line
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and connect them
with the straight edge. There are several ways to do this. |
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We outline two
common methods. |
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Intercept
method: |
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| If we let
x = 0, the y intercept is 3y = 2 or |
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and if
we let y =0 the x intercept is (1,0) |
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Slope-Intercept
method: |
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| Solving
for y in the form y = mx + b we get: |
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| From this
form we see that the y intercept is |
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| From this
point we can use the slope, which is |
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to find a second
point by moving, 2 units to the left (0 – 2 = – 2) |
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| and 3 units
up |
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to get
the second point |
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