Question #N682
A function f is defined by the equation $f(x) = 3x^2 - 5$. If $f(a) = 22$, what is the value of $a$?
A. -3
B. -1
C. 1
D. 3
Correct Answer is: D
Substitute 22 for $f(a)$ in the equation to get $22 = 3a^2 - 5$. Add 5 to both sides to get $27 = 3a^2$. Divide both sides by 3 to get $9 = a^2$. Take the square root of both sides to get $a = 3$ or $a = -3$. Since the question asks for the value of $a$, the answer is 3.