Question

if the sum of the first n terms of an AP is 4n - 1 find the common difference?​

Answer 1

Answer:

${s}^{1} = 4n - 1 \\ n = 1 \\ {s}^{1} = 4(1) - 1 = 3 \\ {s}^{2} = 4(2) - 1 = 7 \\ {a}^{1} = {s}^{1} = 3 \\ {a}^{2} = {s}^{2} - {a}^{1} \\ \rightarrow \: 7 - 3 = 4 \\ so \: \: \: \: \: \: \: \\ {a}^{2} = 4 \\ d = {a}^{2} - {a}^{1} = 7 - 4 = 3 \\ therefore \: \\ \bold{\underline{d = 3}}$

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