Question

sendo a1=10, an=-8, r=-3, calcule n.

Answer 1

an = a1 +(n-1)r

-8 = 10 -3n+3

-8 = 13 -3n

-21 = -3n

n= 7

Answer 2

Sendo a1=10, an=-8, r=-3, calcule n.

an = a1 + (n-1).r

10 + (n-1).(-3) = - 8

10 -3n + 3  = - 8

3n = 10 +3 + 8

3n = 21

n = 7