How do you factor completely: $2x^2 − 2x − 40$ ?

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Answer 1 · 2015-07-21T21:23:44

$2(x-5)(x+4)$

First pull out the factor of 2:
$2x^2-2x-40=2(x^2-x-20)$

For the roots we now need numbers $a,b$ that satisfy $ab=-20$ and $a+b=-1$ . This gives $a=4, b=-5$ :
$2(x^2-x-20)=2(x-5)(x+4)$

How do you factor completely: 2x^2 − 2x − 402x^2 − 2x − 40?