#### Answer

$x=-3$ or $x=7$

#### Work Step by Step

We solve by factoring:
$x^{2}-4x=21$
$x^{2}-4x-21=0$
$(x+3)(x-7)=0$
$x+3=0$ or $x-7=0$
So we have: $x=-3$ or $x=7$

Published by
Brooks Cole

ISBN 10:
1305115546

ISBN 13:
978-1-30511-554-5

$x=-3$ or $x=7$

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