(x y-3) (x-4)i=0

1.2(Xy+Xy)-3(Xy-xy)-4Xy=2*2xy-0-4xy=4xy-4xy=02.1/2ab-5aC-(3acb)+(3aC-4aC)=1/2ab-5ac-3acb-ac=1/2ab-6a

1.平方和绝对值的结果都是非负数,所以如果两者加起来等于0就说明两者本身都为0.接下去你知道怎么做了吧2.这题千万别两边直接乘以（x-1)（x+2）,只要把右边通分就可以了,这样分母相同,然后就只需考

即(3x-4y)(x+y)=03x=4y或x=-y若3x=4yy=3x/4则y²=9x²/16,xy=3x²/4原式=(3x²/4-3x²)/(9x&

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

（x+2）^2+|y+1|=0x=-2,y=-15xy²-｛2xy²-[3xy²（4xy²-2x²y）]｝=5xy²-2xy²+3

∵x-3√（xy）-4y=0∴（√x-4√y）(√x+√y)=0∵x,y不能都等于0∴√x=4√y∴x=16y∴（2x+3√(xy)-2y)/(3x-√(xy)+y)=(32y+12y-2y)/(48

因为x-3*根号(xy)-4y=0所以(x-4y)=3*根号(xy)所以(x-4y)^2=9xy展开,合并x^2-17xy+16y^2=0;所以(x-y)(x-16y)=0;所以x=y或者x=16y;

由2x²-3y²=xy得(X+Y)(2X-3Y)=0所以X=-y,或者2X=3Y,当X=-y时,代入得=-5当2X=3Y,代入得=15/14

13x^2-6xy+y^2-4x+1=0(9x^2-6xy+y^2)+4x^2-4x+1=0(3x-y)^2+(2x-1)^2=0加数均非负,和为0.则均为0所以有：3x=y2x-1=0x=1/2y=

3x+4y=0,即x=-4y/32xy+y²/x²-xy=2y(-4y/3)+y²/(-4y/3)²-(-4y/3)y=(-5/3)y²/(28/9)

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

|x+3|+(y-1/3)的平方=0|x+3|=0,(y-1/3)的平方=0x=-3y=1/33x²y-[2xy²-2(xy-2/3x²y)-xy]+3xy²=

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

x²-3xy+4x=3,y²+xy-4y+7=0相加得x²-2xy+y²+4（x-y）+4=0（x-y）²+4（x-y）+4=0（x-y+2）=0,得

①xy同非负时,2x-3√xy-2y=(2√x+√y)(√x-2√y)=0∴√x=2√y,x=4y②xy同负时,2x-3√xy-2y=[2√(-x)+√(-y)][√(-x)-2√(-y)]=0∴√(

2x-3√(xy)-2y=0(2√x+√y)(√x-2√y)=0因为x>0,xy≥0所以y≥02√x+√y>0所以√x-2√y=0,即x=4y(x^2+4xy-16y^2)/(x^2+xy-9y^2)

Ix-2I+(y+1)²=0,绝对值与平方均为非负数,则有x=2,y=-15x²+3xy-5y²-2xy+4y²-4x²=x^2-y^2+xy=4-1

∵x-y=4xy∴原式=[2(x-y)+3xy]/[-(x-y)-2xy]=(8xy+3xy)/(-4xy-2xy)=11xy/(-6xy)=-11/6

2x^2-3xy-2y^2=0（x-2y)(2x+y)=0x-2y=0或2x+y=0x=2y或y=-2x当x=2y时(4x^2-5xy+y^2)/(3x^2+3xy+y^2)=（4×4y²-