Question

numa pg dados a1=2g=5 e an=1250,calcule n

Answer 1

$a_1=2\\ q=5\\ a_n=1250\\\\ a_n=a_1.q^{n-1}\\\\ 1250=2.5^{n-1}\\\\ 2.5^{n-1}=1250\\\\ 5^{n-1}=\frac{1250}{2}\\\\ 5^{n-1}=625\\\\ 5^{n-1}=5^4\\\\ n-1=4\\ n=5$