SOLUTION: Given: {{{S=(2*PI*r*h)+(2*PI*r^2)}}}, solve for r.

Algebra ->  Human-and-algebraic-language -> SOLUTION: Given: {{{S=(2*PI*r*h)+(2*PI*r^2)}}}, solve for r.      Log On


   

Question 13423: Given: S=%282%2API%2Ar%2Ah%29%2B%282%2API%2Ar%5E2%29, solve for r.
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
You could try this:
S+=+2%28pi%29rh+%2B+2%28pi%29r%5E2 Factor 2%28pi%29 and divide both sides by it.
S%2F2%28pi%29+=+rh+%2B+r%5E2 Subtract S%2F2%28pi%29 from both sides.
r%5E2+%2B+hr+-+S%2F2%28pi%29+=+0 Solve for r using the quadratic formula.
r+=+%28-h%2B-sqrt%28%28-h%29%5E2+-+4%28-S%2F2%28pi%29%29%29%29%2F2
r+=+%28-h%2B-sqrt%28h%5E2%2B%282S%2F%28pi%29%29%29%29%2F2