已知x和y的真值,求[x y]补=-搜答案-智慧作业帮

(x-xy)-(xy-y)=40-(-20)x-xy-xy+y=40+20x+y-2xy=60(x-xy)+(xy-y)=40+(-20)x-xy+xy-y=40-20x-y=20

x-xy=8(1)xy-y=-9(2)则有(1)-(2):X-XY-XY+Y=X+Y-2XY=8-(-9)=17

依题意得,xy+(x+y)=71xy*(x+y)=880则xy,(x+y)为方程t^2-71t+880=0的两根.∴xy=55,x+y=16或xy=16,x+y=55∴x^2+y^2=(x+y)^2-

-xy（x^2y^5-xy^3-y)=-(xy^2)^3+(xy^2)^2+xy^2=-(-2)^3+4-2=8+4-2=10

XY除于X加Y等于3,则XY=3(X+Y)2X-3XY+2Y的和除于-X+3XY-Y=2X-9(X+Y)+2Y的和除于-X+9(X+Y)-Y=-7(X+Y)÷8(X+Y)=-7/8再问：是除于X+Y的

前两个式子相减：x-xy-（xy-y）=x+y-2xy=5-（-3）=8

x-y=(x-xy)+(xy-y)=40+(-20)=20x+y-2xy=(x-xy)-(xy-y)=60希望满意!

参考不知道对不对x-y=6得x-y的平方=36x-y的平方等于x平方+y平方-2xy所以116--2xy＝36所以-2xy＝-80所以xy就等于40

x=1,y=任意数

令x=sinay=cosa(1-xy)(1+xy)=1-（xy）^2=1-(sinacosa)^2=1-1/4sin(2a)^2显然0《（sin2a）^2《13/4《1-1/4sin(2a)^2《1即

(x+y):y=8:33x+3y=8y得3x=5y设x=5a,y=3a所以(2x+5y)/(3x-y)=(10a+15a)/(15a-3a)=25a/12a=25/12(x^2-xy)/(y^2+3x

x^2-xy=60,xy-y^2=40,x^2-y^2=(x^2-xy)+(xy-y^2)=60+40=100x^2-2xy+y^2=(x^2-xy)-(xy-y^2)=60-40=20

x^2-xy=60为（1）式xy-y^2=40为（2）式则x^2-y^2=（1）+（2）=60+40+100x^2.-2xy+y^2=（1）-（2）=60-40=20再问：为什么再答：==！这个应该显

x²+y²=19(x+y)²=x²+y²+2xy=25xy=3(x-y)*(x-y)=(x-y)²=x²+y²-2xy=

∵x²-xy=60;xy-y²=40.x(x-y)=60;y(x-y)=40x-y=60/x;y*60/x=40y/x=2/3y=2/3x;x=3/2yx²-xy=60x

x^2+2xy+y^2=(x^2+xy)+(y^2+xy)=8+2=10x^2-y^2=(x^2+xy)-(y^2+xy)=8-2=6

=8……（1）=3……(2)(1)+(2)=x^2-xy+xy-y^2=x^2-y^2=11（1)-(2)=x^-2xy+y^2=x^2-xy-（xy-y^2)=x^2-xy-xy+y^2=5

x^2-xy与xy-y^2相比各个式子提取公因式（x-y）求得x/y=3/2两个等式相加就是x^2-y^2=100因式分解（x+y）*（x-y）=100将x=3y/2带入求得y的平方是20可以x的平方

x-y=(x-xy)+(xy-y)=40+(-20)=20x+y-2xy=(x-xy)-(xy-y)=60