(5x^2-7y^2)(7y^2+5x^2)怎么算

解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7 (2x-3y)-(5x-y)怎么算 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 3x+2y=7 5x-y=3 怎么算 化简2（2X-7Y)(7Y+2X)+X^2-(-4X+5Y)(-5Y-4X) 数学(x-y)^5*(y-x)^3*(x-y)^2 (1)(x^2+y)(-y+x^2)-(-x)^2·(-x^2) (2)(5x-3)(5x+3)-3x(3x-7) 怎么 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 5(2x-7y)-(4x-10y)全过程 5x+2y=83x-y=7 合并同类项：-3x+2y-5x-7y