Hour of Math · SS1 · Unit FMP6

The Sum of a Finite Geometric Series

Derive S_n = a(r^n - 1)/(r - 1) by shifting and subtracting, use both forms for ratios above and below 1 and for negative ratios, find sums from two given terms, find how many terms give a sum, and choose the correct ratio in increasing or decreasing G.P. problems.

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