当x y=5,x-y=3时,3x平方-5y平方=

(x-y)^3=x³--3x²y+3xy²-y³得-3x²y+3xy=²(x-y)^3-(x³-y³)原式=x(x&su

(xy+2y)-(x+2)/x^2-4=【y(x+2)-(x+2)】/(x+2)(x-2)=(y-1)/(x-2)=(7-1)/(3-2)=6

=(x³＋y³)＋xy(x＋y)=(x＋y)(x²－xy＋y²)＋xy(x＋y)=(x＋y)(x²＋y²)=(x＋y)[(x＋y)²

原式=2x+(7-7k)xy+3y^2+5y不含则系数为0所以7-7k=0k=1

当k=__3__时,x²-kxy与y²+3xy-5的和不含xy项3-k=0;所以k=3；手机提问的朋友在客户端右上角评价点【满意】即可.再问：谢谢你~

|y-x|-2|xy|=|-3-(-2)|-2|-2×(-3)|=|-1|-2|6|=1-2×6=1-12=11很高兴为您解答,【学习宝典】团队为您答题.请点击下面的【选为满意回答】按钮,

3xy-[2xy-2(xy-2分之3xy)+xy]+3xy=6xy-[2xy-2xy+3xy+xy)=6xy-4xy=2xy=2×3×3分之1=2

x^4-xy^3-x^3y-3x^2y+3xy^2+y^4=x^4-x^3y-3xy(x-y)+y^4-xy^3=x^3(x-y)-3xy(x-y)-y^3(x-y)=(x-y)(x^3-3xy-y^

x^4-xy^3-x^3y-3x^2y+3xy^2+y^4=（x^4-x^3y）-xy^3+y^4-3x^2y+3xy^2=x^3(x-y)-y^3(x-y)-3xy(x-y)=x^3-y^3-3xy

=3x^2y-2xy^2+2(xy-3/2x^2y)-xy+3xy^2=3x^2y+xy^2+2xy-3x^2y-xy=xy+xy^2=3*(-1/3)+3*1/9=-2/3

当x=-4y=-2时求代数式-3x平方y+3xy平方+x?+3x平方y-3xy平方-y,=-3x²y+3xy²+x-y+3xy(x-y)=-3xy(x-y)+(x-y)+3xy(x

1/x-1/y=5y-x=5xy(3x+5xy-3y)÷(x-3xy-y)=(-15xy+5xy)/(-5xy-3xy)=-10xy/(-8xy)=5/4

(3x-4y+2xy)--(2x--5y+5xy)=3x-4y+2xy-2x+5y-5xy=x+y-3xy=5-3*(-3)=5+9=14

-3x^2y^2+2y-2x=2（y-x）-3x^2y^因为X-Y=2,XY=3所以y-x=-2x^2y^=9带入上士=2*（-2）-3*9=-4-27=-31会了不?自己认真学.小屁孩.不好好学习.

原式分子分母同除以y²原式=[(xy+y²)/y²]/[(x²-xy)/y²]=[(x/y)+1]/[(x/y)²-(x/y)]=(3/4+

√x(√x+√y)=3√y(√x+5√y)x-2√xy-15y=0(√x-5√y)(√x+3√y)=0因为x>0,y>0所以√x=5√yx=25y代入后式得到：[2x+(√xy)+3y]/[x+(√x

2(xy-5xy的平方)-(3xy的平方-xy)＝2xy-10xy的平方-3xy的平方＋xy＝3xy-13xy的平方当x=-1,y=1时,原式＝-3＋13＝10

(x+y)(x-y)+（x-y）²-（x²-3xy）=x²-y²+x²-2xy+y²-x²+3xy=x²+xy=x(x+

xy+5kxy=0,k=-1/5

(9x^2y-6xy^2)÷(-3xy)-【(4y^2-9x^2)/(-3x+2y)】=-3x+2y-【(2y-3x)（2y+3x）÷(-3x+2y)】=-3x+2y-2y-3x=-6x=-6×（-1