How do you factor 3h2+19h+20?

1 Answer
Jun 2, 2015

f(h)=3h2+19h+20

Let's use AC Method, with a twist...

A=3, B=19, C=20

Look for a factorization of AC=320=60 into a pair of factors whose sum is B=19.

The pair B1=4, B2=15 works.

Then for each of the combinations A, B1 and A, B2, divide by the HCF (highest common factor) to get the coefficients of a factor of f(h)...

(A,B1)=(3,4) (HCF 1)(3,4)(3h+4)
(A,B2)=(3,15) (HCF 3)(1,5)(h+5)

So f(h)=3h2+19h+20=(3h+4)(h+5)