Question

numa p.g,dados a1=2q=5e an=1250,calcule n

Answer 1

a1=2q=5e an=1250,calcule n


2.5^(n-1) = 1250

5^(n-1) = 1250 ==> 5^(n-1) = 625 ==> 5^(n-1) = 5^4
                   2
n - 1 = 4 ==> n = 4+1 ==> n = 5

Answer 2

resolução!

an = a1 * q^n - 1

1250 = 2 * 5^n - 1

1250/2 = 5^n - 1

625 = 5^n - 1

5^4 = 5^n - 1

n - 1 = 4

n = 4 + 1

n = 5