tanA+tanB=-3/2tanA*tanB=-7/2tan(A+B)=(tanA+tanB)/(1-tan(A+B))=-3/2*2/9=-1/3
tana+tanb=-3/2tanatanb=-7/2tan(A+B)=(tanA+tanB)/(1-tanAtanB)=(-3/2)/(1+7/2)=-1/3
设两根分别x1、x2原式=(x1+x2)/(1-x1x2)由韦达定理得x1+x2=-3/2 x1x2=-7/2代入解得答案