Lets express the algebraic expression given below in reduced from:

Given

But we know, , so the above expression becomes

But we know (x² - y²) = (x + y)(x - y), so the above expression becomes,

Now cancelling the like terms, we get

⇒ = (p + q)(x - y)

By opening the brackets, we get

⇒ = p(x - y) + q(x - y)

⇒ = px - py + qx - qy

Hence