若X2 +y2 -4x-6y= -13 求分式x2-2y2/2xy的值

若X2 +y2 -4x-6y= -13 求分式x2-2y2/2xy的值

(x^2-4x+4)+(y^2-6y+9)=0

(x-2)^2+(y-3)^2=0

x-2=0
y-3=0

x=2
y=3

x2-2y2/2xy=(2^2-2*3^2)/(2*2*3)=-7/6

x2+y2-4x-6y+13=0

=> x2-4x+4 + y2-6y+9 =0
=> (x-2)^2 + (y-3)^2=0

所以x=2,y=3

带入后面的分式中，求去吧！

X2 +y2 -4x-6y+13=0

配方

(x-2)的平方+(y-3)的平方=0
所以x=2 y=3

4-18/12=4-1.5=2.5

若X2 +y2 -4x-6y= -13
(x-2)^2+(y-3)^2=0
x=2
y=3
x2-2y2/2xy=4-2*9/(2*2*3)=4-3/2=5/2