Question

Find the GCF of each expression. Then factor the expression. 25b^2 - 20b

Answer 1

$25b^2-20b=5b(5b-4)$

Answer 2

Hello!

The prime factors of these two numbres are :

$25b^2 = 5^2\times b^2\\ 20b = 5\times 2^2 \times b$

The GCF can be calculated by multiplying common primes factors :
$5\times b = 5b$

So the GCF is 5b and the expression can be factored this way :
$25b^2 - 20b = 5b\times 5b - 4\times 5b = 5b\left(5b-4\right)$