How do you factor $n^2-9n+20$ ?

Question

3515 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2015-05-28T11:39:43

$n^2-9n+20=(n-4)(n-5)$

Here you can use the quadratic formula:
let $p(n)=an^2+bn+c$
$Delta=b^2-4ac$
$n_(1,2)=(-b+-sqrt(Delta))/(2a)$
Then $p(n)=a(n-n_1)(n-n_2)$ .

In our case we have $a=1, b=-9, c=20$ so
$Delta=1, n_1=4, n_2=5$

How do you factor n^2-9n+20n^2-9n+20?