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Multiple Choice
Find the general formula for the arithmetic sequence below. Without using a recursive formula, calculate the 30th term. {−9,−4,1,6,…}
A
46
B
136
C
146
D
150
Verified step by step guidance
1
Identify the first term (a₁) of the arithmetic sequence. In this case, the first term is -9.
Determine the common difference (d) by subtracting the first term from the second term. For this sequence, d = (-4) - (-9) = 5.
Write the general formula for the nth term of an arithmetic sequence: aₙ = a₁ + (n - 1) * d. Substitute the values of a₁ = -9 and d = 5 into the formula.
Simplify the formula to get the explicit expression for the nth term: aₙ = -9 + (n - 1) * 5.
To find the 30th term (a₃₀), substitute n = 30 into the formula: a₃₀ = -9 + (30 - 1) * 5. Simplify the expression to calculate the value of the 30th term.