已知3x y-4=0,则3xy的值最大值为
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由,X/3+Y/4=1得y=4-4x/3.故求xy的最大值即求:xy=x(4-4x/3)=4x-4/3*x^2的最大值.根据抛物线性质易求得最大值即为顶点处.
x2-xy=-3①,2xy-y2=-8②,①×2+②×3得:2x2-2xy+6xy-3y2=-6-24=-30,则2x2+4xy-3y2=-30.
y-x-2xy=0y-x=2xyx-y=-2xy(3x+xy-3y)/(y-xy-x)=[3(x-y)+xy]/[(y-x)-xy]=(-6xy+xy)/(2xy-xy)=-5xy/xy=-5
-xy(x^2y^5-xy^3-y)=-(xy^2)^3+(xy^2)^2+xy^2=-(-2)^3+4-2=8+4-2=10
原式=3xy+6y-xy+6x=2xy+6(x+y)=2*(-2)+6*4=24-4=20
∵2(x2+xy)-3(xy+y2)=2x2-xy-3y2,∴2x2-xy-3y2=2×3-3×(-2)=12.故选A.
因为x-y=4xy所以x-2xy-y=2xy2x+3xy-2y=11xyx-2xy-y分之2x+3xy-2y=5.5
已知2x-3*根号(xy)-2y=0(x>0),则x2+4xy-16y2除以2x2+xy-9y2的值是多少?2x-3*根号(xy)-2y=0(根号X-2根号Y)(2根号X+根号Y)=0根号X-2根号Y
(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
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
条件是(x+1)^2+|y-1|=0,是吗?如果是它的话,那么x=-1,y=1.带入原式,得值为2
y-x-2xy=0所以x-y=-2xyy-x=2xy所以原式=[3(x-y)+xy]\[(y-x)-xy]=[3×(-2xy)+xy]\(2xy-xy)=-5xy\xy=-5
∵x-y=4xy,∴2x+3xy-2yx-2xy-y=2(x-y)+3xyx-y-2xy=8xy+3xy4xy-2xy=112.故答案为:112.
根据题意,2x2-3xy+y2=0,且xy≠0,故有(yx)2−3yx+2=0,即(yx−1)(yx−2)=0,即得yx=1或2,故xy=1或12,所以xy+yx=2或212.故选A.
(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-y=4xy∴原式=[2(x-y)+3xy]/[-(x-y)-2xy]=(8xy+3xy)/(-4xy-2xy)=11xy/(-6xy)=-11/6