m²=n+2 ①n²=m+2 ②①-②得(m-n)×(m+n)=n-mm+n=-1①×m=m³=mn+2m ③②×n=n³=mn+2n ④③④带入得m³-2mn+n³=mn+2m-2mn+mn+2n =2×(m+n)=-2
m²=n+2n²=m+2相减得(m-n)(m+n+1)=0,m≠n,即m+n=-1m³-2mn+n³=(m+n)(m²-mn+n²)-2mn=-1()往下推