In each of the following find the pdf of Y and show that the pdf integrates to 1.
a) f_X(x) = 1/2 e^-|x|, -∞ < x < ∞; Y = |X|^3
b) f_X(x) = 3/8 (x + 1)^2, -1 < x < 1; Y = 1 - X^2
c) f_X(x) = 3/8 (x + 1)^2, -1 < x < 1; Y = 1 - X^2 if X ≤ 0 and Y = 1 - X if X > 0