在有差和形式的极限中为何不能随意使用等价无穷小

比如说某个变化趋势下有两对等价无穷小量F(x)～G(x),f(x)～g(x),考察余项F(x)-G(x)=o(F(x))=o(G(x)),f(x)-g(x)=o(f(x))=o(g(x)),F(x)+f(x) = G(x)+o(G(x)) + g(x)+o(g(x)) = [G(x)+g(x)]+[o(G(x))+o(g(x))]到这里为...