已知4X-3Y-3Z=0和X-3Y-Z=0 ,求x²+y²-z²分之xy+2yz的值
问题描述:
已知4X-3Y-3Z=0和X-3Y-Z=0 ,求x²+y²-z²分之xy+2yz的值
答
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