How do you factor 16p² -4pq - 30q²?

1 Answer
Jun 3, 2015

16p^2-4pq-30q^2 is homogeneous of order 2, so is amenable to the AC Method for quadratics.

16p^2-4pq-30q^2 = 2(8p^2-2pq-15q^2)

A=8, B=2, C=15

Look for a factorization of AC=8*15=120 into two factors whose difference is B=2.

The pair B1=10, B2=12 works.

Now, for each of the pairs (A, B1) and (A, B2) divide by the HCF (highest common factor) to yield coefficients of factors of our quadratic, choosing signs for the terms appropriately.

(A, B1) = (8, 10) -> (4, 5) -> (4p+5q)
(A, B2) = (8, 12) -> (2, 3) -> (2p-3q)

Hence

16p^2-4pq-30q^2 = 2(4p+5q)(2p-3q)