How does (xy - ab) = b(x-a)+(x-a)(y-b)+a(y-b)?

Question

I know how to work the RHS to equal the LHS

bx - ba + xy - xb -ay + ab + ay - ab = xy - ab

I've posted this twice already but everyone's been showing me how to expand the RHS. hehe..

What I really wanna know is how to work from the LHS (xy - ab) to arrive to b(x-a)+(x-a)(y-b)+a(y-b).

Thanks =)

Answer 1

You can't really go from the left hand side to the right hand side.

It's like saying... Show that 2 is equal to 3842904832843843903 - 3842904832843843901 - (2 root 3 + 5 root 36) + 2 root 3 + 30. You can simplify the latter and show that the answer is 2, but you can't work from the former and show that it is equal to the latter. I hope you know what I mean.

I hope that helps. :)

me07.