【x+y】分之xy=-2,
xy分之【x+y】=-1/2
1/x+1/y=-1/2 (1)
【y+z】分之yz=3分之4,
yz分之【y+z】=3/4
1/y+1/z=3/4 (2)
【z+x】分之zx=-3分之4,
zx分之【z+x】=-3/4
1/x+1/z= -3/4 (3)
(1)+(2)+(3),
得,2(1/x+1/y+1/z)= -1/2
则,1/x+1/y+1/z = -1/4
即,xyz分之 【xy+yz+zx】= -1/4
所以,【xy+yz+zx】分之xyz =-4