Q. Find an explicit formula for the arithmetic sequence170,85,0,−85,…Note: the first term should be d(1).d(n)=
Identify Type: Identify whether the given sequence is geometric or arithmetic. The sequence 170, 85, 0, −85, ... has a common difference between consecutive terms, so it is an arithmetic sequence.
Find First Term & Difference: Determine the first term (d(1)) and the common difference (d) of the sequence. The first term is 170, and by subtracting the second term from the first term, we find the common difference: 85−170=−85.
Use Explicit Formula: Use the explicit formula for an arithmetic sequence, d(n)=d(1)+(n−1)d, where d(1) is the first term and d is the common difference. For this sequence, d(1)=170 and d=−85.
Substitute Values: Substitute the values of d(1) and d into the formula to write an explicit formula for the sequence. The formula for the sequence is d(n)=170+(n−1)(−85).
Simplify Formula: Simplify the formula by distributing the common difference. The simplified formula is d(n)=170−85(n−1).
Further Simplify: Further simplify the formula by multiplying out the terms. The simplified formula is d(n)=170−85n+85.
Combine Like Terms: Combine like terms to get the final explicit formula for the sequence. The final formula is d(n)=255−85n.
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