添空題已知數列{an}中a3=2,a7=1,又數列{an}是等差數列,則a8=?

添空題已知數列{an}中a3=2,a7=1,又數列{an}是等差數列,則a8=?

a3=a1+N*2=2 a7=a1+N*6=1解得等差數列{an}的公差N=-1/4則a8=a7+N=3/4