(1+(n/m)-(n/m-n))除以(1-(n/m)-(m/m+n))=[(m²-mn+mn-n²-mn)/(m-n)]÷[(m²+mn-mn-n²-m²)/(m+n)]=(m²-mn-n²)/(m-n)÷(-n²)/(m+n)=(m²-mn-n²)(m+n)/n²(n-m)=(...