Set the factored derivative equal to zero. Then, set each factor equal to zero and solve for x to identify the critical values. 4x(x-2)(x-4) = 0 If 4x = 0, then x = 0 If x-2=0, then x = 2x x Your answer cannot be understood or graded. More Information If x 4 0, then x = 4x Your answer cannot be understood or graded. More Information.