SOLUTION: Find the radius of a cylinder with a height of 8 cm and a surface area of 96(pi)cm^2.

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Question 157294This question is from textbook Saxon Algebra 2
: Find the radius of a cylinder with a height of 8 cm and a surface area of 96(pi)cm^2. This question is from textbook Saxon Algebra 2

Answer by jojo14344(1513) About Me  (Show Source):
You can put this solution on YOUR website!
Remember: Area%5Bc%5D=2%28pi%29%28r%5E2%29%2B2%28pi%29%28r%29%28h%29 ------> working eqn
Substitute:
%2896cm%5E2%29%28pi%29=2%28pi%29%28r%5E2%29%2B2%28pi%29%28r%29%288%29

48=r%5E2%2B8r
r%5E2%2B8r-48=0, factor out, perfect square:
%28r%2B12%29%28r-4%29=0
2 values: r=-12 ------------> don't use, (-)
r=4cm ----------------------> RADIUS, to be used
In doubt? go back working eqn:
%2896%29pi=2%28pi%29%284%5E2%29%2B2%28pi%29%284%29%288%29
%2896%29pi=32%28pi%29%2B64%28pi%29
%2896%29pi=%2896%29pi
Thank you,
Jojo