7.6
39.Concept Check In which one of the following does yvary inversely as x?A. B. C. D.Solve each problem.
40.For the subject in a photograph to appear in the
same perspective in the photograph as in real life,
the viewing distance must be properly related to the
amount of enlargement. For a particular camera, the
viewing distance varies directly as the amount of
enlargement. A picture that is taken with this cam-
era and enlarged 5 times should be viewed from a
distance of 250 mm. Suppose a print 8.6 times the
size of the negative is made. From what distance
should it be viewed?
41.The frequency (number of vibrations per second) of a vibrating guitar string varies in-
versely as its length. That is, a longer string vibrates fewer times in a second than a shorter
string. Suppose a guitar string 0.65 m long vibrates 4.3 times per sec. What frequency
would a string 0.5 m long have?
42.The volume of a rectangular box of a given height is proportional to its width and length.
A box with width 2 ft and length 4 ft has volume Find the volume of a box with the
same height, but that is 3 ft wide and 5 ft long.12 ft^3.y= y=x^23
xy=x
3y= 2 x422 CHAPTER 7 Rational Expressions and Functions
MIXED REVIEW EXERCISES
Write in lowest terms.Perform the indicated operations.45. 46. 47.
48. 49. 50.
51. 52.
53. 54.
Solve.
- for r
57. 58.
3 x
x- 4+
2
x=
48
x^2 - 4 x1 -
5
r=
- 4
r^2A=
Rr
R+rx+ 3
x^2 - 5 x+ 4-
1
x=
2
x^2 - 4 xa
b+
b
c+
c
d4 a
a^2 - ab- 2 b^2-
6 b-a
a^2 + 4 ab+ 3 b^29 x^2 + 46 x+ 5
3 x^2 - 2 x- 1,
x^2 + 11 x+ 30
x^3 + 5 x^2 - 6 xk^2 - 6 k+ 9
1 - 216 k^3#^6 k
(^2) + 17 k- 3
9 - k^2
t-^2 +s-^2
t-^1 - s-^1
4 y+ 16
30
,
2 y+ 8
53
x- 5
6 +
1
x- 3
x- x
2
- x
1 +
x+ 1
x9
3 - x-
2
x- 32
m+
5
3 m^2x^2 + 2 x- 15
x^2 - x- 6x+ 2 y
x^2 - 4 y^2