已知4x-3y-6z=0,x+2y-7y=0(xyz≠0),求代数式5x^2+2y^2-z^2/2x^2-3y^2-10z^2的值.
问题描述:
已知4x-3y-6z=0,x+2y-7y=0(xyz≠0),求代数式5x^2+2y^2-z^2/2x^2-3y^2-10z^2的值.
答
4x-3y-6z=0(1)x+2y-7z=0(2)(1)-(2)3x-5y+z=0z=5y-3x代入(1)4x-3y-30y+18x=022x=33y2x=3y设x=3k,则y=2kz=10k-9k=k所求代数式=(45k²+8k²-k²)/(18k²-12k²-10k²)=52/(-4)=-13...