Evaluating Variable Expressions

9.7.1 Evaluating Variable Expressions

9.7.1 • Evaluating Variable Expressions

Evaluate each expression for $a = 9$ , $b = - 5$ , and $c = - 2$ .

What is the value of $- b$ ?

$- (- 5) = 5$

What is the value of $b^{2}$ ?

$(- 5)^{2} = 25$

What is the value of $b^{2} - 4 a c$ ?

$(- 5)^{2} - 4 (9) (- 2) = 25 - (36) (- 2) = 25 - (- 72) = 25 + 72 = 97$

Select two answers for $- b \pm \sqrt{a}$ .

$- (- 5) + \sqrt{9} = 5 + 3 = 8$ and $- (- 5) - \sqrt{9} = 5 - 3 = 2$

The correct answers are 2 and 8: $- (- 5) + \sqrt{9} = 5 + 3 = 8$ and $- (- 5) - \sqrt{9} = 5 - 3 = 2$