两式相加得m^2+n^2=6两式相减得mn=2(m^2+n^2)^2-2(mn)^2=28
(m+n)^2=m^2+n^2+2mn=10(m-n)^2=m^2+n^2-2mn=2两式相减得4mn=8mn=2二式相加得m^2+n^2=[10+2]/2=6m^4+n^4=(m^2+n^2)^2-2m^2n^2=6*6-2*2*2=28