Question

已知m平方=n+2,n平方=m+2(m不等于n),求m立方-2mn+n立方的值解释

Answer 1

m^3-2mn+n^3

=m(n+2)-2mn+n(m+2)

=mn+2m-2mn+mn+2n

=2(m+n)

m^2-n^2=n+2-(m+2)=n-m

(m-n)(m+n)=n-m

m+n=-1

原式=-2