m/(m+n)+m/(m-n)-n²/((m²-n²)=(m²-mn+m²+mn-n²)/(m²-n²)=(2m²-n²)/(m²-n²) [分子分母同时除以n²]=[2(m/n)²-1]/[(m/n)²-1]=1+(m/n)&sup...