a₁ = 8
d = 5
n = 15
a₁₅ = a₁ + 14d = 8 + 14 * 5 = 8 + 70 = 78
ответ : a₁₅ = 78
an=a1+d(n-1)
an=8+5(15-1)
an=8+70
an=78
a₁ = 8
d = 5
n = 15
a₁₅ = a₁ + 14d = 8 + 14 * 5 = 8 + 70 = 78
ответ : a₁₅ = 78
an=a1+d(n-1)
an=8+5(15-1)
an=8+70
an=78