Find the interval in which the function 'f' defined by `f(x) = -2x^3 -9x^2 - 12x + 1` is strictly increasing

Find the interval in which the function 'f' defined by f(x) = 2x^3 -8x^2 + 10x + 3 is strictly decreasing

Find the intervals in which the function f, given by f(x)=-2x^(3)-9x^(2)-12x+1 is strictly increasing and strictly decreasing.

Find the intervals in which the function f, given by f(x)=2x^(3)-3x^(2)-36x+7 is strictly increasing and strictly decreasing.

Find the intervals in which the function f given by f(x)=2x^(3)-3x^(2)-36x+8 is (i) strictly increasing (ii) strictly decreasing