SOLUTION: The square of a number is equal to 15 more than the twice number. Find all such number.

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Question 1144184: The square of a number is equal to 15 more than the twice number. Find all such number.
Answer by ikleyn(52794) About Me  (Show Source):
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x^2 = 2x + 15


x^2 - 2x - 15 = 0.


(x-5)*(x+3) = 0


The roots are x= 5  and  x= -3.


Answer.  There are 2 (two) such numbers, 5 and -3.