设函数f(x)=ax+b,其中a,b为实数,f1(x)=f(x),fn+1(x)=f(fn(x)),n=1,2,3…若f7(x)=128x+381,求a+b?

x��)�{�n����ϦnHӨдM��N�yں�Ɏ��:IOv�z�nPN'�$R���� ��
iM�<[C#�G �^t/M3�YTh[�<�ؔ��do�T�O'���l��4��{:*���|�gnb��6�g�����V\Z`d� �Dډqf@%I@50C��#����4 mj�_\��g�v ��