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Use the formula for the sum of a geometric sequence to evaluate 42 + 43 + 44 + ... + 4m.

A) 42(4ᵐ - 1)/(3)
B) 42(4ᵐ - 1)/(4)
C) 42(4ᵐ + 1)/(3)
D) 42(4ᵐ + 1)/(4)

1 Answer

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Final answer:

The sum of the given geometric series is found using the formula for the sum of a geometric sequence, resulting in option A: 42(4m - 1)/(3) as the correct answer.

Step-by-step explanation:

The question asks us to use the formula for the sum of a geometric sequence to evaluate the series 42 + 43 + 44 + ... + 4m. The formula for the sum of a geometric sequence is Sn = a(1 - rn)/(1 - r), where Sn is the sum of the series, a is the first term, r is the common ratio, and n is the number of terms.

In this series, our first term a is 42 (or 16), the common ratio r is 4, and the number of terms is m - 1 since the series starts at the second term of the sequence. Applying the sum formula, we get:

S = 16(1 - 4m-1)/(1 - 4) = 16(4m-1 - 1)/(-3), after simplifying we have:

S = 16(1 - 4m-1)/(-3) = 16(1/(-3)) * (4m/4 - 1) = 42(4m - 1)/(3).

Therefore, the correct option is A: 42(4m - 1)/3

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