已知 x y=3 4 x-y=1 4-搜答案-灵鹊做题网

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

题有问题吧,是X+XY+Y=14吧?如果是的话x+xy+y+y+xy+x=42合并一下（X+Y）+x+y=42设x+y=a则a+a=42a=6或a=-7

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

已知x+3xy-y=0则x-y=-3xy所以x-2xy-y分之2x-14xy-2y=[(x-y)-2xy]/[2(x-y)-14xy]=[-3xy-2xy]/[2*(-3xy)-14xy]=(-5xy

y-x=3xyx-y=-3xy(x-2xy-y)/(2x-14xy-2y)=(-3xy-2xy)/(-3xy*2-14xy)=-5xy/(-20xy)=1/4

xy/(x+y)=2∴xy=2(x+y)(3xy-x-y)/(3x-5xy+3y)=[6(x+y)-x-y]/[3x+3y-10(x+y)]=5(x+y)/[-7(x+y)]=-5/7

（1）∵xy+x=-1①，xy-y=-2②，∴①-②得x+y=1；（2）先把xy+x=-1，xy-y=-2的值代入代数式，得原式=-x-[2y-1+3x]+2[x+4]=-x-2y+1-3x+2x+8

∵y-x=3xy∴x-y=-3xy∴(2x-14xy-2y)/(x-2xy-y)=[2(x-y)-14xy]/[(x-y)-2xy]=(-6xy-14xy)/(-3xy-2xy)=(-20xy)/(-

此题主要是把x-y用-3xy代替就可作了x-2xy-y/2x-14xy-2y=(-3xy-2xy)/2(x-y)-14xy=-5xy/(-6xy-14xy)=-5xy/-20xy=1/4

2(x+xy)-[(xy-3y)-x]-(-xy)=2x+2xy-xy+3y+x+xy=3x+3y+2xy=3（x+y）+2xy=3*（-2）+2*3=0

x+3xy-y=0∴x-y=-3xy2x-14xy-2y/x-2xy-y=[(2x-2y)-14xy]/[(x-y)-2xy]=[2(x-y)-14xy]/[(x-y)-2xy]=(-6xy-14xy

∵x-y=4xy，∴2x+3xy-2yx-2xy-y=2(x-y)+3xyx-y-2xy=8xy+3xy4xy-2xy=112．故答案为：112．

xy+1/xy>=2√（xy*1/xy）=2(当xy=1/xy即xy=1时取等号)x/y+y/x>=2√（x/y*y/x）=2(当x/y=y/x即x=y取等号)当x=y=1时可以同时满足两项的等号要求

因为xy/（x+y）=1/2所以x+y=2xy原式=3（x+y)-5xy/(-x-y+3xy)=3*2xy-5xy/(-2xy+3xy)=xy/xy=1

16524

3(x^2-xy)-xy+y^2=3(x^2-xy)-(xy-y^2)=3*5-(-3)=15+3=18

x^2-xy=14,(1)xy-y^2=-11,(2)(1)-(2)得：x^2-2xy+y^2=14-(-11)=25

原式=-xy²（x²y^4-xy²-1）∵xy²=-2原式=2（（-2)²-（-2）-1）=10

∵x+3xy-y=0∴x-y=-3xy\x102x-14xy-2y/x-2xy-y\x10=[2(x-y)-14xy]/[(x-y)-2xy]\x10=(-6xy-14xy)/(-3xy-2xy)\x