Please don't write nonsense: cx^2 is NOT equal to 2 cx. Yes, I know what you MEANT but that was what you wrote. Also the power rule does not apply to "all functions".hawaiidude posted or you can use teh "good" old lim h~~>0 f(x+deltax)-f(x)/ delta x...in your case f(x)=-2(x-3)^3 ....or you can use the power rule for all functions cx^2=2cx