SOLUTION: the book says to solve by factoring and using the principle of zero products: x2+4x-21=0 how do you do this?

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Question 371342: the book says to solve by factoring and using the principle of zero products:

x2+4x-21=0
how do you do this?
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!


Hi,

solve by factoring and using the principle of zero products

x^2+4x-21=0

factoring

(x+7)(x-3) = 0  Note: the SUM of the outer product,-3x and inner product,7x = 4x

using the principle of zero products

(x+7= 0

x = -7

(x-3) = 0

x = 3