Answer:
Below.
Step-by-step explanation:
i) (a + b)^2 = a^2 + 2ab + b^2
= (x + y)^2 + 2(x + y)(x - y) + (x - y)^2
= x^2 + 2xy + y^2 + 2(x^2 - y^2) + x^2 - 2xy + y^2
= x^2 + 2x^2 + x^2 + y^2 - 2y^2 + y^2 + 2xy - 2xy
= 4x^2.
ii) (a - b)^2 = a^2 + b^2 - 2ab
= (x + y)^2 + (x - y)^2 - 2 - 2(x^2 - y^2)
= x^2 + 2xy + y^2 + x^2 - 2xy + y^2 - 2x^2 + 2y^2
= x^2 + x^2 - 2x^2 + y^2 + y^2 + 2y^2 + 2xy - 2xy
= 4y^2.
