韦达定理
tanα+tanβ=3
tanαtanβ=-3
tan(α+β)=(tanα+tanβ)/(1-tanαtanβ)=3/4
tan(2α+2β)
=tan[2(α+β)]
=2tan(α+β)/[1-tan²(α+β)]
=24/7
tanα+tanβ=3 ,tanαtanβ=-3
tan(α+β)=(tanα+tanβ)/(1-tanαtanβ)=3/4
tan(2α+2β)=2tan(α+β)/[1-tan^2(α+β)]
=2*(3/4)/[1-(3/4)^2]
=24/7