Question 414181
The derivative of f(x) is given by


{{{(d/dx)f(x) = 3x^2 + 20x + 25}}} (applying the power rule)


The critical points occur when {{{(d/dx)f(x) = 0}}}, i.e.


{{{3x^2 + 20x + 25 = 0}}}


{{{x = (-20 +- sqrt(400 - 300))/6 = (-20 +- 10)/6}}} = -5/3 and -5. f(5) = -125 + 250 + (-125) - 50 = -50, so (-5, -50) is the other critical point (sorry I accidentally replaced -5 into f'(x) instead of f(x) so I just revised my answer).