31 R.3 Real Number Operations and Properties EXAMPLE 6 Using Order of Operations Evaluate each expression for x = -2, y = 5, and z = -3. (a) -4x2 - 7y + 4z (b) 21x - 522 + 4y z + 4 (c) x 2 - y 5 3z 9 + 8y 5 SOLUTION (a) -4x2 - 7y + 4z = -41-222 - 7152 + 41-32 Substitute: x = -2, y = 5, and z = -3. = -4142 - 7152 + 41-32 Evaluate the exponential. = -16 - 35 - 12 Multiply. = -63 Subtract. (b) 21x - 522 + 4y z + 4 = 21-2 - 522 + 4152 -3 + 4 Substitute: x = -2, y = 5, and z = -3. = 21-722 + 4152 -3 + 4 Work inside the parentheses. = 21492 + 4152 -3 + 4 Evaluate the exponential. = 98 + 20 1 Multiply in the numerator. Add in the denominator. = 118 Add; a 1 = a (c) x 2 - y 5 3z 9 + 8y 5 Work separately above and below the main fraction bar. = -2 2 - 5 5 31-32 9 + 8152 5 Substitute: x = -2, y = 5, and z = -3. = -1 - 1 -1 + 8 Simplify the fractions. = - 2 7 Subtract and add; -a b = - a b S Now Try Exercises 99, 107, and 109. Use parentheses around substituted values to avoid errors.
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