Here's the question you clicked on:
ahoymewmew
what is the factor of this trinomial a2 + 4ab – 45b2?
Because it is + then - we know it needs to be in the form ( a + b )( a - b )
I would first look at the coefficient of b^2 which as 45 and write down all the numbers when multiplied will give you 45.
Then look at these numbers and see which two when added will give you 4. And excuse my last post, I should have said find all the products that will give you -45
Let me know if you are still stuck
@ChmE so you multiply all the products that equal to 45 and then add the two that will give you 4?
That is a thought process for solving it. 9,-5 -9,5 1,-45 -1,45 I think thats it. Then you think what numbers, when added will give me 4. you see 9,-5
and if you look at my first post, you see the form it needs to be is consistent with these numbers. So ( a + 9b ) ( a - 5b )