How do you factor x^2+4x=21?

1 Answer
Jim G.
May 18, 2017

(x+3)(x-7)

Explanation:

"rearrange and equate to zero"

rArrx^2+4x-21=0

"to factor we can 'split' the middle term"

rArrx^2+4x-21

=x^2+3x-7x-21

"taking out a common factor gives"

=color(red)(x)(x+3)color(red)(-7)(x+3)

"take out " (x+3)" as a common factor"

=(x+3)(color(red)(x-7))

rArrx^2+4x-21=(x+3)(x-7)

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