等差数列{an}中,a2=40,a14=124,则a1=?,d=?
问题描述:
等差数列{an}中,a2=40,a14=124,则a1=?,d=?
答
a14-a2=12d
a14-a2=124-40=84
12d=84
d=7
a1=a2-d=40-7=33
答:a1=33 d=7