如果x:y=2:3,求(x^2+xy+2y^2)/(x^2-xy+y^2)的值
问题描述:
如果x:y=2:3,求(x^2+xy+2y^2)/(x^2-xy+y^2)的值
答
(x^2+xy+2y^2)/(x^2-xy+y^2)
=[(x/y)²+(x/y)+2]/[(x/y)²-(x/y)+1] 分子分母同时除以y²
=(4/9+2/3+2)/(4/9-2/3+1)
=28/7
=4