1.If a + b = x and ab = y, express (a − b)^2 in terms of x and y.

(A) x^2 − y (B) x2 ^− 2y (C) x^2 − 4y (D) x^2 + 2y (E) x^2 − y^2

if i apply the formula for (a − b)^2 then i dont get any of the answers.the problem comes as to where a+b=x should be used.

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 ?