Solve each of the following systems of equations by the method of cross-multiplication:
(a−b)x+(a+b)y=2a2−2b2
(a+b)(x+y)=4ab
x=2ab−a2+b2b,y=(a−b)(a2+b2)b(a+b)
Solve the equation by substitution method :
(a+b)x + (a+b)y = 2a2 -2b2
(a+b) (x + y) = 4ab