Question

(x+y)(2x+y)+(x+2y)(x-y) ​

Answer 1

(x+y)(2x+y)+(x+2y)(x−y)

=x(2x+y)+y(2x+y)+x(x−y)+2y(x−y)

=2x³+xy+2xy+y²+x² −xy+2xy−2y²

=(2+1)x²+(1+2−1+2)xy+(1−2)y²

=3x²+4xy²