Sum of first n terms of a GP (If r is not 1, S_n = a(1−r^n)/(1−r); if r=1, sum is na)
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If r is not 1, S_n = a(1−r^n)/(1−r); if r=1, sum is na
What each symbol means
| Symbol | What it stands for |
|---|---|
| S_n | Sum of first n terms |
| a,r,n | As in GP |
When to use this
Separate case r=1; for r≠1 denominator 1−r must not be zero.