So from the first eqaution, we get

Hence,

2.Simplify (−a − b) 2 − (a + b)(a − b) .

i get ANSWER

-(a^2+2ab+b^2)-a^2-b^2=-2a^2-2ab=-2a(a-b)

But the actual answer is 2b^2 + 2ab.How ?

the minus sign in front of was your problem. it is not the same as what you had before. squaring gets rid of the negative