Question

(a + b - c)(a + b + c)

Answer 1

maybe mult. terms like this

a(a+b+c) =?
b(a+b+c)=?
-c(a + b + c)=?

try that and then we can combine like terms

Answer 2

a

Answer 3

i will do the firstline

a^2 + ab+ac

you do the 2nd line

Answer 4

simplify?

Answer 5

do you see now??