Geometric Sequence Calculator
The calculator will find the terms, common ratio, sum of the first $$$n$$$ terms and, if possible, the infinite sum of the geometric sequence from the given data, with steps shown.
Related calculator: Arithmetic Sequence Calculator
Your Input
Find $$$a_{4}$$$, $$$S_{3}$$$, $$$S_{\infty}$$$, given $$$a_{1} = 3$$$, $$$r = 5$$$.
Solution
We have that $$$a_{1} = 3$$$.
We have that $$$r = 5$$$.
$$$a_{4} = a_{1} r^{4 - 1} = 3 \cdot 5^{4 - 1} = 375$$$
$$$S_{3} = \frac{a_{1} \left(1 - r^{3}\right)}{1 - r} = \frac{3 \left(1 - 5^{3}\right)}{1 - 5} = 93$$$
Since $$$\left|{r}\right| = 5 \geq 1$$$, the infinite sum is infinite.