dx/dt = -4x-2x^2

find the find the maximum rate of change of x (t)

i know its could be very easy but i just have no ideas at all

---------------------------------------

give the values of n and C for which y=Cx^n is a solution of the equation x^3 dy/dx -10 x^2 y =0

the answer is, C=0 and n could be any no. , but why?

thx