分组求和求和 2+(x+y)/xy+(x^2+y^2)/x2y2+(x^3+y^3)/x^3y^3+.+(x^n+y^n
求和(x+1/y)+x^2+1/y^2)+...+(x^n+1/y^n)(x,y不等于0)
求和:(x+1/y)+[x^2+1/(y^2)]...+[x^n+1/(y^n)](x,y不等于1)
求和(x+1/y)+x^2+1/y^2)+...+(x^n+1/y^n)(x,y不等于0) 急.
(x+y)+(2x+1/1*2y)+(3x+1/2*3y)+.+(9x+1/8*9y) x=2 y=90求和
[x(x^2y^2-xy)-y(x^2-x^3y)]/3x^2y
x^3+3x-4,4x^2+2x-y-y^2,x^3-y^3-x^2y+xy^2.求分组分解法分解因式
(x+y)(x-y)-(2xy+3y)平方
1、(-7x^y)(2x^y-3xy^3+xy) 2、((x-y)^6)/((y-x)^3)/(x-y)
化简:x-y/x+3y÷x^-y^2/x^2+6xy+9y^2-(xy/x+y)
已知M=(x+y)/(Öx-Öy)-2xy/(xÖy-yÖX),N=(3Öx-2Öy)/[Ö(x+y)+Ö(y-x)].
(2x+3y)(4x+5y)(2x-3y)(5y-4x) 如何分组
(x-2xy)*(-xy+2y*y)-(3x*x-2xy)(x-9xy+6y*y)