(x + 2y)(x + 2y) - (x - y)(x + 3y)
= 2(x + 2y) - (x2 + 3xy - xy - 3y2)
= 2x + 4y - x2 - 2xy - 3y2
= 2x + 4y - x2 - 2xy - y2 - 2y2
= 2(x + 2y) - (x + y)2 - 2y2
= 2(x + 2y) - (x + y - 2y)(x + y + 2y)
= 2(x + 2y) - (x - y)(x + 3y)
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(x+2y) (x+2y) - (x-y) (x+3y)
=x^2+2xy+2xy+4y^2-(x^2+3xy-xy-3y^2)
=x^2+2xy+2xy+4y^2-x^2-3xy+xy+3y^2
=x^2-x^2+4y^2+3y^2+2xy+2xy-3xy+xy
=7y^2+2xy
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