# Homework Help: Difference of squares

1. Jan 19, 2008

### rocomath

I'm looking for patterns and if you can add to things I noticed before working it out, that would be good :-]

1. $$(a+b+c)(a+b-c)=a^2+b^2+c^2+2ab$$

I noticed that b+c and b-c compensated for each other.

2. $$(a+b+c)(a-b-c)=a^2-b^2-c^2-2bc$$

a+b and a-b compensated for each other and the fact that it's b+c and -b-c, is the reason that it was -2bc?

3. $$(a+b-c)(a-b+c)=a^2-b^2-c^2+2bc$$

a+b and a-b compensated for each other, Now I figured from problem 2 that it would be 2bc again, but I didn't predict the sign correctly?

Last edited: Jan 19, 2008
2. Jan 19, 2008

### rock.freak667

Not sure I will be helpful here but all I can see is that
$$(a+b+c)(a-b-c)==(a+(b+c))(a-(b+c))=(a)^2-(b+c)^2$$

and the same for the 3rd one.

for the first one:
$$(a+b+c)(a+b-c)((a+b)+c)((a+b)-c)$$