SOLUTION: The product of two consecutive integers is 90 less than twice the square of the next larger integer. Find the smaller integer.
A. 6
B. 8
C. 10
D. 12
Question 1198815: The product of two consecutive integers is 90 less than twice the square of the next larger integer. Find the smaller integer.
A. 6
B. 8
C. 10
D. 12 Found 2 solutions by math_tutor2020, ikleyn:Answer by math_tutor2020(3835) (Show Source): You can put this solution on YOUR website!
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.