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Finding the 50th term
Find the 50th term of the sequence 7,11,15,19,...
First, identify a1=7 and d=4 (each term increases by 4). Then use the formula: a50=7+(50−1)×4=7+196=203.
Without the formula, you would need to compute 49 additions. With the formula, you get the answer in one step. This is the power of closed-form expressions.
