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The sum of an integer and its square is 90. Find the number

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JustinJakeAshtonviz
The integer is 9.
9 + 9^2 (or 81) = 90.
Equation: Let the integer be x.

x² + x = 90

Equate to zero to solve the quadratic equation:
x² + x - 90 = 0

Factor: 
(x + 10) (x - 9) = 0

Solve for roots (x):
x + 10 = -10                      x - 9 = 0
x = -10                              x = 9

Choose the positive root, x = 9, the integer.

To check:
(9)² + 9 = 90
81 + 9 = 90
90 = 90