(1.) f(x)=x^3+3x^2-2x+15. (a.) find the differential of f(x) (b.) hence find the gradient of f(x) when x=6 (c.) is f(x) increasing or decreasing at this point?
(1.) (a.) f’(x)=3x^2+6x-2
(b.) x=6 gradient=142
(c.) since f’(x)>0 at x=6, the function is increasing.
