Question

Which of the following is an even function? (A) g(x)=5x+2 (B) g(x)=x (C) g(x)= x 2 (D) g(x)=x3 (E) g(x)=−|x|

Answer 1

(C) g(x) = x² and (E) g(x) = -|x|

Explanation:

If f(x) is an even function, then f(-x) = f(x).

(A)

g(x) = 5x + 2

g(-x) = 5(-x) + 2 = -5x + 2

g(-x) ≠ g(x)

(B)

g(x) = g(x) = x

g(-x) = -x

g(-x) ≠ g(x)

(C)

g(x) = x²

g(-x) = (-x)² = (-1x)² = (-1)²(x)² = x²

g(-x) = g(x)

(D)

g(x) = x³

g(-x) = (-x)³ = (-1x)³ = (-1)³(x)³ = -1x³ = -x³

g(-x) ≠ g(x)

(E)

g(x) = -|x|

g(-x) = -|-x| = -|-1x| = -(|-1|)(|x|) = -1|x| = -|x|

g(-x) = g(x)