How do you factor the expression $x^2 +7x-8$ ?

Question

23274 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-05-12T09:52:50

$x^2+7x-8 = (x-1)(x+8)$

Given $x^2+7x-8$

Note that the sum of the coefficients is $0$ . That is $1+7-8 = 0$ .

So $x=1$ is a zero and $(x-1)$ a factor:

$x^2+7x-8 = (x-1)(x+8)$

The linear factor $(x+8)$ can be constructed by looking at the coefficients of $x^2$ and the constant term $-8$ that we want in the product:

Since the coefficient of $x^2$ is $1$ in the product, we require a coefficient $1$ for $x$ .
Since the constant term is $-8$ in the product, we require a constant $+8$ in the factor which will become $-8$ when multiplied by $-1$ .

How do you factor the expression x^2 +7x-8x^2 +7x-8?