(x+2y)(x+3y)+(x-2y)的二次方+(x-3y)的二次方

问题描述:

(x+2y)(x+3y)+(x-2y)的二次方+(x-3y)的二次方

(x+2y)(x+3y)+(x-2y)^2+(x-3y)^2
=x^2+5xy+6y^2 +x^2-4xy+4y^2 +x^2-6xy+9y^2
=3x^2-5xy+19y^2