已知2x+3y-5z=0,3x-2y+12z=0(z≠0),求4x²-12xy+9y²/2x²-3xy
问题描述：
已知2x+3y-5z=0,3x-2y+12z=0(z≠0),求4x²-12xy+9y²/2x²-3xy
答
2x+3y-5z=0,(1)
3x-2y+12z=0 (2)
(1)*12+(2)*5得：
(24+15)x+(36-10)y=0
39x+26y=0
3x=-2y
y/x=-3/2
4x²-12xy+9y²/2x²-3xy
=(2x-3y)²/[x(2x-3)]
=(2x-3y)/x
=2-3y/x
=2+9/2
=13/2