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JAMB Mathematics 2019 Paper

Question : 29

Total: 73

^{2n - 1}

. Find the sum of the first four terms.

Solution:

Concept:

The given formula defines a geometric progression because each term is multiplied by a common ratio.

Explanation:

Given

T_n = 2^{2n-1}

Substitute

n = 1

T_1 = 2^{2(1)-1} = 2^1 = 2

Substitute

n = 2

T_2 = 2^{2(2)-1} = 2^3 = 8

Substitute

n = 3

T_3 = 2^{2(3)-1} = 2^5 = 32

Substitute

n = 4

T_4 = 2^{2(4)-1} = 2^7 = 128

This sequence has first term

a = 2

and common ratio

r = 4

Sum of the first four terms is

2 + 8 + 32 + 128

Answer:

170

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