Friday, November 16, 2012

College Algebra, Chapter 1, 1.3, Section 1.3, Problem 62

Solve A=2πr2+2πrh for r.


A=2πr2+2πrhGivenA=2π(r2+rh)Factor out 2πA2π=r2+rhDivide both sides by 2πA2π+h24=r2+rh+h24Complete the square: add (h2)2=h24A2π+h24=(r+h2)2Perfect square±2A+h24π=r+h2Take the square root and simplify by using LCDr=h2±2A+h24πSubtract h2r=h2±12(2A+h2π)Solve for r

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