Solve the given boundary-value problem.
y'' + 2y = 6x, y(0) = 0, y(1) + y'(1) = 0

a) y(x) = 3x - x²
b) y(x) = -3x² + 6x
c) y(x) = -x² + 2x
d) y(x) = 2x - x²