SOLUTION: (1/2)r(r+1)-36=0

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Question 262600: (1/2)r(r+1)-36=0
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
(1/2)r(r+1)-36=0
r(r+1)/2=36
r^2+r=72
r^2+r-72=0
r^2 +9r-8r-72=0
r(r+9) -8(r+9)=0
(r+9)(r-8)=0
R= -9 or 8
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