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WAEC Mathematics 2012 Paper

Question : 5

Total: 49

The n^th term of a sequence is T_n = 5 + (n - 1)². Evaluate T₄ - T₆

Solution:

Concept:

Substitute the given value of

n

into the formula for the

n^{th}

term, then subtract the results.

Explanation:

Given

T_n = 5 + (n-1)^2

For

n=4

T_4 = 5 + (4-1)^2 = 5 + 3^2 = 5 + 9 = 14

For

n=6

T_6 = 5 + (6-1)^2 = 5 + 5^2 = 5 + 25 = 30

Now evaluate

T_4 - T_6 = 14 - 30 = -16

Answer:

T_4 - T_6 = -16

, so the correct option is C. -16.

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