已知 x y=3 4 x-y=1 4
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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
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