What is the factors for $x^2-x-20$ ?

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Answer 1 · 2018-03-24T20:52:31

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

What factors of $-20$ add up to the value of b which is $-1$ ?:
$4, -5$

$-4, 5$

$10, -2$

$-10, 2$

$20, -1$

$-20, 1$

It would be $4, -5$ , therefore:
$(x-5)(x+4)$ , since a is equal to 1

Answer 2 · 2018-03-24T20:54:15

$x^2-x-20 = (x+4)(x-5)$

$x^2-x-20$

In order to factor, we have to find factors of $-20$ that when summed together give us $-1$ (since $-1$ is the coefficient of the middle term).

Factors of $-20$ :
$(-1, 20),(1,-20),(2,-10),(-2, 10),(-4,5),color(blue)(((4,-5)))$

We see that $(4,-5)$ has two factors for $-20$ that when summed together equals $-1$ .

So we can write our factor form:

$x^2-x-20 = (x+color(blue)(4))(xcolor(blue)(-5))$

What is the factors for x^2-x-20x^2-x-20?