已知xy满足x² y²-8x 6y 9=0 求x²+y²-搜答案-智慧作业帮

一、x²y-xy²-x+y=56xy(x-y)-(x-y)=56(xy-1)(x-y)=56将xy=8代入：7(x-y)=56x-y=8①又x²+y²=(x-y

x方y-xy方-x+y=56xy(x-y)-x+y=568(x-y)-x+y=567x-7y=56x-y=8x^2+y^2=(x-y)^2+2xy=64+2*8=80

再问：该方法此处计算是错的，应该为，接下来的都不对了再答：那就从那步开始吧x+y=xy-8若x，y大于0xy-8=x+y≥2√xyxy-8≥2√xyxy-2√xy-8≥0(√xy-4)(√xy+2)≥

依据约束条件,画出可行域.直线x+2y-3=0的斜率k1=-1/2,目标函数z=ax+y(a＞0)对应直线的斜率k2=-a,若符合题意,则须k1＞k2,即-1/2＞-a,得a＞1/2.

(x+y)^2=(x-y)^2+4xy=64+4(-z^2-16)=-4z^2=0所以(x+y)^2=0所以x+y=0x-y=8x=4,y=-4z=0

∵正数xy满足x+2y=2,∴2=x+2y=x/2+x/2+2y≥3[³√(x²y/2)]即³√(x²y/2)≤2/3,x²y/2≤8/27,x

在线数学帮助你：这是一道关于化简求解的题目；根据题目给出的式子：X^2Y-XY^2-X+Y=56；提出XY；XY（X-Y）-（X-Y）=56；再提出（X-Y）可得；（XY-1）（X-Y）=56；因为X

x.x.y-x.y.y-x+y=xy(x-y)-(x-y)=(xy-1)(x-y)=7(x-y)=56所以x-y=8x^2+y^2=(x-y)^2+2xy=64+16=80

由2x^2+4xy+4y^2+8x+12y+10=0得x^2+2xy+2y^2+4x+6y+5=0x^2+2(y+2)x+(y+2)^2-(y+2)^2+2y^2+6y+5=0(x+y+2)^2+(y

2X+Y

S=x^2+y^2+2x-2y+2化为(x+1)^2+(y-1)^2=S圆心为(-1,1)且经过约束区域的最小圆的半径就是S,这可以通过画图确定.

因为X-Y=8所以X.Y的值会出现4种情况1.X为正,Y为负X+|Y|=82.X为负,Y为负|Y|-X=83.X为正,Y为正X-Y=84.X为负,Y为正Y-X=8又有条件了个条件:XY+Z2=-16那

xy=8x^2y-xy^2-x+y=568x-8y-x+y=567x-7y=56x-y=8x^2+y^2=(x-y)^2+2xy=8^2+2*8=64+16=80所以,x^2+y^2=80

z=3x+y=13(x+2y)/6+5(x-4y)/6当x=5,y=2时取到,z最大值17

1因为xy=8,x*x*y-x*y*y-x+y=56直接把xy=8代进去可以得到8x-8y-x+y=56x-y=8跟xy=8联立方程得到x、y的值（自己算）2x*x+y*y+z*z-x*y-y*z-x

将xy=8代入x平方y-8xy平方-x+y=56得8x-8y-x+y=56x-y=8x平方+y平方=(x-y)^2+2xy=8^2+2*8=64+16=80

x²y-Xy²-x+y=56xy(x-y)-(x-y)=56(x-y)(xy-1)=56因为xy=8所以x-y=56/(xy-1)=56÷7=8x²+y²=(x

(x+y)^2=(x-y)^2+4xy=64+4(-z^2-16)=-4z^2=0所以(x+y)^2=0所以x+y=0x-y=8x=4,y=-4z=0

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