# The sum of a positive integer and its square is 90.Find the integer

2
by Oracionangelica

2015-10-15T20:08:55+08:00

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9.
9 - (positive integer), 81 - (square of the integer)
9 + 81 = 90.
• Brainly User
2015-10-16T07:01:53+08:00

### This Is a Certified Answer

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Let the positive integer be x

The sum of the positive integer and its square is 90:
x + x² = 90

x² + x - 90 = 0

Solve the quadratic equation by factoring:
(x + 10) (x - 9) = 0

x + 10 = 0                    x - 9 = 0
x = -10                         x = 9

Choose the positive root, x= 9.

The positive integer is 9.

To check:

x + x² = 90

9 + (9)² = 90
9 + 81 = 90
90 = 90