SOLUTION: x^2-4x=21 solve for x

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Question 658497: x^2-4x=21
solve for x
Found 2 solutions by checkley79, nerdybill:
Answer by checkley79(3341) About Me  (Show Source):
You can put this solution on YOUR website!
x^2-4x=21
X^2-4X-21=0
(X-7)(X+3)=0
X-7=0
X=7 ANS.
X+3=0
X=-3 ANS.
PROOFS:
-7^2-4*-7=21
49+28=21
21=21
-3^2-4*-3=21
9+12=21
21=21

Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
x^2-4x=21
x^2-4x-21=0
factoring the left side:
(x+3)(x-7) = 0
x = {-3, 7}