Question

.а1=10;S14=1050.Найдите  a2

Answer 1

((a₁+a₁₄)*14)/2=1050
a₁+a₁₄=1050*2:14
a₁+a₁₄=150
10+a₁₄=150
a₁₄=140
a₁+13d=140
10+13d=140
13d=130
d=130:13
d=10
a₂=a₁+d=10+10=20