53.Suppose that the directions on a test read “Solve the following expressions.” How would
you politely correct the person who wrote these directions?
54.Suppose that, for the equation the value of xis given as 4. What would be
the corresponding value of y? How do you know this?
Decide whether the given number is a solution of the equation. See Example 4.
- ;1 56. ;1
- ;3 58. ;2
- ; 60. ;
- ;4 62. ;3
- ;2 64. ;5
- ;20 66. ;40
Write each word statement as an equation. Use x as the variable. Find all solutions from the
set See Example 5.
67.The sum of a number and 8 is 18.
68.A number minus three equals 1.
69.Sixteen minus three-fourths of a number is 13.
70.The sum of six-fifths of a number and 2 is 14.
71.One more than twice a number is 5.
72.The product of a number and 3 is 6.
73.Three times a number is equal to 8 more than twice the number.
74.Twelve divided by a number equals times that number.
Identify each as anexpressionor anequation.See Example 6.
A mathematical modelis an equation that describes the
relationship between two quantities. For example, the life
expectancy at birth of Americans can be approximated by
the equation
where x is a year between 1943 and 2005 and y is age in
years. (Source: Centers for Disease Control and Prevention.)
Use this model to approximate life expectancy (to the
nearest tenth of a year) in each of the following years.
- 1943 82. 1960
- 1985 84. 2005
85.How has the life expectancy at birth of Americans
changed in the years from 1943 to 2005?
y=0.212x-347,9 r+ 31 r- 42 = 2 x+y= 9 x+y- 93 x+ 21 x- 42 8 y- 13 y+ 52 7 t+ 21 t+ 12 = 41
35 2, 4, 6, 8, 10 6.
0.5 1 x- 42 = 80 0.2 1 x- 52 = 707
10
x+1
2
= 4
3
8
x+1
4
= 1
3 r^2 - 2 = 46 2 x^2 + 1 = 1912
5
2 x+ 3 x+ 8 = 201
5
6 p+ 4 p+ 9 = 112 y+ 31 y- 22 = 14 6 x+ 21 x+ 32 = 144 m+ 2 = 6 2 r+ 6 = 83 x-y=9,