Question

How can this be factored
a^2-2ab-8b^2

Answer 1

@marird15

Do you know how to factor a^2 - 2a - 8? I realize that is not the question asked but the factoring technique is similar.

Answer 2

Great. Would you post that here? Then, we can relate it to your question?

Answer 3

(a-4)(a+2)
^^Post this up?

Answer 4

Correct. Look at your work:
a^2 - 2a - 8 = (a-4)(a+2)

Compare that to the trinomial you want to factor:

a^2-2ab-8b^2. How do they differ. Compare term by term.

Answer 5

the second one has two variables A and B

Answer 6

Yes. Think about the problem as:

(a)^2 - 2 (a)(b) - 8 (b)^2

-4 and 2 will still be part of the factorization but will have to have the variable b with them.

Any ideas on how to do that? Play with it a bit.

Answer 7

Hint: (a - ? ) * (a + ?) = a^2-2ab-8b^2

Answer 8

You know you need the -4 and the 2. You also need to account for the variable b.

Answer 9

What does -4b times 2b equal?

Answer 10

- 8b
wouldn't it be (a-4b)(a+2b)
?

Answer 11

-4b times 2b equals - 8b^2.
And, yes, (a-4b)(a+2b) = a^2-2ab-8b^2
Very good.

Answer 12

Yaay! okay thank u ! i understand now

Answer 13

Great. Thanks for hanging in there with me as we went through the process. It was fun.

Answer 14

Question? @marird15 Or, another problem to work?

Answer 15

oh no thanks that was it! :) @Directrix