Solve each of the following problems by separation of variables.

x. 5x^2 = x, x = 25 (0)
a. -4x^2 = x, x = 36 (0)
xx. -5x = x, x = 25 (0)
d. 2e^(-4t)x = x, x = 0 (0)

a) x = 5
b) x = 6
c) x = -5
d) x = 2e^(4t)