Is the solution wrong? I checked and the numerator does not have root 3. It seems the function does not have any minimum value
The solution for August 17th
Hi Victoria. Thanks for pointing this out! In fact the problem was meant to have $x^3+3x^2-10x - 24$ (with $-24$ instead of $+24$). Then things work out nicely (with the polynomial division having no remainder). The question and solution are now updated.
Please let us know if you have any other questions!