已知x 4y=-1xy=5
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令F(XY)=1/XY+XY,当XY=1的时候,F(XY)=2,最小.(可由函数图形象得出).XY趋于正无穷大的时候F(XY)趋于正无穷大,XY无限趋于零的时候F(XY)趋于正无穷大.所以XY越接近1
-xy(x^2y^5-xy^3-y)=-(xy^2)^3+(xy^2)^2+xy^2=-(-2)^3+4-2=8+4-2=10
(x+2)^2+|y+1|=0x=-2,y=-15xy²-{2xy²-[3xy²(4xy²-2x²y)]}=5xy²-2xy²+3
x^2y+xy^2=xy(x+y)=1/5
5xy+4x+7y+6x-3xy-4xy+3y=5xy-3xy-4xy+4x+6x+7y+3y=(5-3-4)xy+(4+6)x+(7+3)y=-2xy+10x+10y=-2xy+10(x+y)因为x
解(x+1)平方+/y-1/=0∴x+1=0,y-1=0∴x=-1,y=1∴2(xy-5xy平方)-(3xy平方-xy)=(2xy+xy)+(-10xy平方-3xy平方)=3xy-13xy平方=3×(
(x+1)平方+y-1的绝对值=0x+1=0y-1=0x=-1y=12(xy-5xy平方)-(3xy平方-xy)=2xy-10xy^2-3xy^2+xy=3xy-13xy^2=-3+13=10
(x+1)^2+|y-1|=0(x+1)^2>=0|y-1|>=0x+1=0,y-1=0x=-1,y=12(xy-5xy的平方)-(3xy的平方-xy)=2xy-10xy^2-3xy^2+xy=3xy
(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
(x+1)^2+|y-1|=0x+1=0x=-1y-1=0y=12(xy-5xy^2)-(3xy^2-xy)=2xy-10xy²-3xy²+xy=3xy-13xy²=3x
xx+2xy-yy=-3两式相加即可
∵x2+xy=5,xy+y2=-1,∴(x2+xy)-(xy+y2)=x2+xy-xy-y2=x2-y2=5-(-1)=6.故填:6
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
∵(x+1)²+|y-1|=0∴x+1=0,y-1=0∴x=-1,y=1∴2(xy-5xy²)-(3xy²)-(3xy²-xy)=2xy-10xy²-
(x+y)^2>=0,(y-1)^2>=0,因此y=1,x=-1.原式=2(-1-5)-(-3+1)=-10再问:打错了是已知(x+1)的平方+(y-1)的绝对值=0,求2(xy-5xy的平方)-(3
3(x^2-xy)-xy+y^2=3(x^2-xy)-(xy-y^2)=3*5-(-3)=15+3=18
(x+1)²+|y-1|=0两个非负数的和为0,这两个非负数都为0x+1=0,y-1=0x=-1,y=12(xy-5xy²)-(3xy²-xy)=2xy-10xy
原式=-xy²(x²y^4-xy²-1)∵xy²=-2原式=2((-2)²-(-2)-1)=10