若x.y满足方程组x-2y=1,x+y=根号3,求代数式x²-xy-2y²-2的值,
问题描述:
若x.y满足方程组x-2y=1,x+y=根号3,求代数式x²-xy-2y²-2的值,
答
x^2-xy-2y^2-2
=(x-2y)(x+y)-2
=sqrt3-2