4x^4y-5x^2y-9y^2

1) (2x+5y)(2x-5y)(-4x^2-25y^2) 2) [（x+y)(x-y)-(x-y)^2+2y(x-y 已知X.x+y.y-4x+2y+5=0,求4X.X-12X Y+9Y.y的值 x^2-y^2/x+y-4x(x-y)+y^2/2x-y, （x+2)(x+3) (x-4)(x+1) (y+4)(y-2) (y-5)(y-3) 已知4x=9y求(1)x+y/y (2)y-x/2x 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 {(z+y)(x-y)-(x-y)的2次方+2y(x-y)}除以4y 计算(x^8-x^7y+x^5y^3-x^4y^4+x^3y^5-x^y^7+y^8)(x^2+xy+y^2) x^8-x^7y+x^6y^2-x^5y^3+x^4y^4-x^3y^5+x^2y^-xy^7+y^8 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? 3(x-y)-2(x+y)-5(x-y)+4(x+y)+3(x-y) 化简合并同类项 (2x-y)^2-4(x-y)(x+2y)