I assume that IS the derivate and you just want the equation solved
\(0 = {{\pi x(10(\sqrt{225-x^2}+15)-x^2})\over{\sqrt{225-x^2}}}\\ 0 =\frac{{\pi x(\sqrt{10\sqrt{225-x^2}+15)}+x)(\sqrt{10\sqrt{225-x^2}15)}-x})}{{\sqrt{225-x^2}}}\\ x=0\:\;\:or\;\;(\sqrt{10\sqrt{225-x^2}+15)}+x)=0\;\;or\;\;(\sqrt{10\sqrt{225-x^2}+15)}-x)=0\\ x=0\:\;\:or\;\;(\sqrt{10\sqrt{225-x^2}+15)}=-x\;\;or\;\;(\sqrt{10\sqrt{225-x^2}+15)}=+x\\ x=0\:\;\:or\;\;10\sqrt{225-x^2}+15=x^2\\ x=0\:\;\:or\;\;\sqrt{225-x^2}=\frac{(x^2-15)}{10}\\ x=0\:\;\:or\;\;225-x^2=\frac{(x^4-30x^2+225)}{100}\\ x=0\:\;\:or\;\;225-x^2=\frac{(x^4-30x^2+225)}{100}\\ x=0\:\;\:or\;\;22500-100x^2=x^4-30x^2+225\\ x=0\:\;\:or\;\;x^4+70x^2-22275=0\\ \)
\(x=0\:\;\:or\;\;x^4+70x^2-22275=0\\ x ^2= {-b \pm \sqrt{b^2-4ac} \over 2a}\\ x ^2= {-70 \pm \sqrt{4900+4*22275} \over 2}\\ x ^2= {-70 \pm \sqrt{94000} \over 2}\\ x ^2\approx {-70 \pm306.6 \over 2}\\ x ^2\approx {-70 \pm306.6 \over 2}\\ x ^2\approx 118.3\\ x\approx \pm10.9\\~\\ so\;I\; get\;\\~\\ x=0\;\;or\;\;x\approx \pm10.9\)
You probably should check those 2 approx answers though. ://
Mmm I do not think it is right.
I am not sure I am answering the right question anyway.://
x=0 is definitely a solution to the question that I answered. ://