1.已知x+y=1,xy=-2,求x^2+y^2+xy/x^2+y^2-xy

来源：学生作业帮编辑：作业帮分类：数学作业时间：2024/07/07 13:31:11

1.已知x+y=1,xy=-2,求x^2+y^2+xy/x^2+y^2-xy
2.x^2-5xy+6^2=0,求x-y/x+y

/>已知x+y=1,xy=-2,求(x²+y²+xy)/(x²+y²-xy)
(x²+y²+xy)/(x²+y²-xy)=[(x+y)²-xy]/[(x+y)²-3xy]=(1+2)/(1+6)=3/7

已知x²-5xy+6y²=0,求(x-y)/(x+y)
将x²-5xy+6y²=0的两边同除以xy,得(x/y)-5+6(y/x)=0；
令x/y=u,则有u-5+6/u=0,即有u²-5u+6=(u-2)(u-3)=0,故u₁=2,u₂=3.
于是得(x-y)/(x+y)=[(x/y)-1]/[(x/y)+1]=(u-1)/(u+1)=1/3或1/2.

已知3/(x-y)=1/xy 求(-x-2xy+y)/ (2x+3xy-2y) 已知x-xy=8,xy-y=-9,求x+y-2xy的值已知：x-y=1,xy=-2.求：(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)的值 .已知:x-y=1,xy=-2.求:(-2xy+2 x+3y)-(3xy+2y-2x)-(x+4y+xy)的值已知x+y=-1,xy=-2,求代数式-5（x+y)+(x-y)+x(xy+y)的值已知:xy+x=-1,xy-y=-2,求多项式-x-[2y-2(xy+x)的平方+3x]+2[x+(xy-y)的平方]的已知xy^2=-2,求-xy（x^2y^5-xy^3-y)的值. 已知xy^2=-2 求-xy(x^2y^5-xy^3-y) 已知x^2-xy=5,xy-y^2=-3求3(x^2-xy)-xy+y^2 已知：xy+x=-1，xy-y=-2．已知X+Y=3XY,求2X+2Y-XY除以X+Y+2XY的值,要算理. 已知x-y=4xy,求x-2xy-y分之2x+3xy-2y的值!