For which of the following functions is f(d) = f(−d) for all values of d ? Choose the correct choice from the following choices.
A) f(x) = x^3 + 3
B) f(x) = −x
C) f(x) = 2x + 3
D) f(d) = −d^2 + 2
E) f(x) = 5x − 4
f(d) = f(−d)   The above is a property of an even function .   f(d) = f^(n)   f(d) = f(−d) will hold when n is an even integer .   The only case when d is even is option f(d) = −d^2 + 2   Answer f(d) = −d^2 + 2
<result>D</result>
For which of the following functions is f(d) = f(−d) for all values of d ?