An=106, n=52, Sn=2860, найти a1, d

Question

An=106, n=52, Sn=2860, найти a1, d

Answer 1

Sn=n(a1+an)/2
52(a1+106)/2=2860
26(a1+106)=2860
a1+106=110
a1=4
an=a1+(n-1)d
106=4+(52-1)d
102=51d
d=2