Question 391047
No need to "estimate" the extrema, since it is easy to find the exact value. Taking the derivative of f(x) and setting it to 0,


{{{d/dx = 3x^2 + 6x = 0}}}, it follows that x = 0 or x = -2 (either by factoring or quadratic formula). We can check a possible extrema by finding the numerical derivative at points less than and greater than the number. If they have different signs then it is an extrema, if they have the same sign, then the function rises until {{{d/dx = 0}}}, then rises again.