计算 ：(2x-5y+3)(2x+5y-3) (x-2y)(x-3y)-(3x-2y)^2

1.(2x-5y+3)(2x+5y-3) 2.(x-2y)(x-3y)-(3x-2y)^2
=[2x-(5y-3)][(2x+(5y-3)] =x^2-5xy+6y^2-(9x^2-12xy+4y^2)
=<4x^2-(5y-3)^2> = -8x^2+7xy+2y^2
=4x^2-25y^2+30y-9 =2y^2+7xy-8x^2

1. (2x-5y+3)(2x+5y-3)
=(2x)^2-(5y-3)^2
=4x^4-25y^2+30y-9
2 (x-2y)(x-3y)-(3x-2y)^2
=(x^2-5xy+6y^2)-(9x^2-12xy+4y^2)
=-8x^2+7xy+2y^2

(2x-5y+3)(2x+5y-3) (x-2y)(x-3y)-(3x-2y)^2
=[4x^2-(5y-3)^2](x^2-5xy+6y^2)-(9x^2-12xy+4y^2)
=4x^4-20yx^3+125xy^3+150y^4+30yx^2-150xy^2+180y^3-9x^2+45xy-54y^2-(9x^2-12xy+4y^2)=4x^4-20yx^3+125xy^3+150y^4+30yx^2-150xy^2+180y^3-18x^2+57xy-58y^2