Question

If the function f is given by f(x)=2x2−4, then which of the following represents the value of c such that f(c)=28? Select one: A. 0 B. 2 C. 4 D. 8

Answer 1

C

given f(x) = 2x² - 4 , then

f(c) = 2c² - 4 = 28 (add 4 to both sides )

2c² = 32 ( divide both sides by 2 )

c² = 16 ( take the square root ob both sides )

c = ± $\sqrt{16}$ = ± 4

Since the answer is looking for the positive solution then c = 4