10r+r^2=120
10r+r^2=120 rearrange
r^2 + 10r - 120pi = 0 ........using the onsite solver, we have...
r2+10×r−120×π=0⇒{r=−√5×√24×π+5−5r=√5×√24×π+5−5}⇒{r=−25.049716168334532r=15.049716168334532}
