若x-y=6,y-z=5,求x²+y²+z²-xy-xz-yz的值.
问题描述:
若x-y=6,y-z=5,求x²+y²+z²-xy-xz-yz的值.
计算题:
1.19.8²-39.6×40.2+40.2²
2.(2分之1a-3b)(3b-2分之1a)
答
x-y=6y-z=5两式相加:x-z=11x²+y²+z²-xy-xz-yz=2(x²+y²+z²-xy-xz-yz)÷2=(2x²+2y²+2z²-2xy-2xz-2yz)÷2=(x²-2xy+y²x²-2xz+z²+y²-2yz+z...