SOLUTION: The square of a number decreased by 4 times the number equals 21. Find the number

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Question 740142: The square of a number decreased by 4 times the number equals 21. Find the number
Answer by powercenter(3) About Me  (Show Source):
You can put this solution on YOUR website!
x= the number
x^2-4x=21
x^2-4x-21=0
(x+3)(x-7)=0
x=-3
x=7