Question

ME AJUDEM!!!! PLEASE 2 Quantos termos Tem a PA (15, 20, ...,795? ?
a) 157
b) 205
C) 138
d) 208​

Answer 1

PA (15, 20, ..., 795)

r = aₙ - aₙ₋₁

r = a₂ - a₁

r = 20 - 15

r = 5

aₙ = a₁ + (n - 1) · r

795 = 15 + (n - 1) · 5

795 = 15 + 5n - 5

795 = 10 + 5n

795 - 10 = 5n

785 = 5n

n = 785/5

n = 157

X) 157

b) 205

C) 138

d) 208​