解方程组：4X-3Y-3Z=0,X-3Y-Z=0,得
x=-6y,z=-9y
x²+y²-z²分之xy+2yz
=[(-6y)*y+2y*(-9y)]/[(-6y)²+y²-(-9y)²]
=-24y²/(-44y²)
=6/11