Q. Find an explicit formula for the arithmetic sequence −5,13,31,49,….. Note: the first term should be b(1).b(n)=
Identify sequence type: Identify whether the given sequence is geometric or arithmetic. The sequence −5,13,31,49,… has a common difference between consecutive terms, so it is an arithmetic sequence.
Determine common difference: Determine the common difference d of the sequence by subtracting the first term from the second term. The common difference is 13−(−5)=18.
Use explicit formula: Use the explicit formula for an arithmetic sequence, b(n)=b(1)+(n−1)d, where b(1) is the first term and d is the common difference. For the sequence −5,13,31,49,…, the first term, b(1), is −5 and the common difference, d, is 18.
Write expression for sequence: Substitute the values of b(1) and d into the formula to write an expression to describe the sequence. The expression for the sequence −5,13,31,49,extellipsis is b(n)=−5+(n−1)imes18.
Simplify expression: Simplify the expression. b(n)=−5+18n−18, which simplifies to b(n)=18n−23.
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