Question

Factorise :
8 + 6(a + b) - 5(a + b)²

Answer 1

8 + 6a + 6b - 5a^2 - 5b^2 - 10ab 

Answer 2

using identities 1st break the (a+b)^2
  then u will get the answer 8+6a+6b-5a^2-5b^2-10ab
                                        hope that it will help u.