Question 1198815
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The first sentence translates to this equation
n(n+1) = 2(n+1)^2-90


n = first integer
n+1 = integer right after n


Let's solve for n.
n(n+1) = 2(n+1)^2-90
n^2+n = 2(n^2+2n+1)-90
n^2+n = 2n^2+4n+2-90
n^2+n = 2n^2+4n-88
0 = 2n^2+4n-88-n^2-n
n^2+3n-88 = 0
(n+11)(n-8) = 0
n+11 = 0 or n-8 = 0
n = -11 or n = 8


If we focus on the positive values only, then n = -11 is ignored.


Answer: Choice B
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