Page 138 - Basic College Mathematics with Early Integers

S E C T I O N 2.1 I INTRODUCTION TO VARIABLES AND ALGEBRAIC EXPRESSIONS 115

61. A number less 5 62. The product of a number and 7

63. 6 divided by a number 64. The sum of a number and 7

65. Fifty decreased by eight times a number 66. Twenty decreased by twice a number

Review

Determine the place value of the digit 7 in each whole number. See Section 1.2.

67. 720 68. 2307

69. 67,522 70. 179

Concept Extensions

Solve. See the Concept Check in this section. Determine whether each expression is correctly evaluated for x = 2 , y = 0 ,
and z = 7 . If incorrect, then correctly evaluate.

71. 2y + 3z 2(2) + 3(7) 72. 2z - 4x 2(7) - 4(2)
4 + 21 14 - 8
25 6

4z 4(7) 2xy 2(2)(0)
73. 74.
2x 2(2) z 7
28 0

4 7
7 is undefined

Use a calculator to evaluate each expression for x = 23 and y = 72.

75. x - y 2 76. 2(x + y) 2
4

2
77. x + 5y - 112 78. 16y - 20x + x 3

79. If x is a whole number, which expression is the 80. If x is a whole number, which expression is the
x x
largest: 2x,5x, or ? Explain your answer. smallest: 2x,5x, or ? Explain your answer.
3 3

81. In Exercise 43, what do you notice about the value of 82. In Exercise 44, what do you notice about the value
16t 2 as t gets larger? 5(F - 32)
of as F gets larger?
9