If Un = n(n 2 + 1), evaluate U5 - U4
MATHEMATICS
WAEC 2013
If Un = n(n2 + 1), evaluate U5 - U4
- A. 18
- B. 56
- C. 62
- D. 80
Correct Answer: C. 62
Explanation
Un = n(n2 + 1)
U5 = 5(2 + 1)
= 5(25 + 1)
= 5(26) = 130
U4 = 4(42 + 1) = 4(16 + 1)
= 4(17) = 68
U5 - U4 = 130 - 68
= 62
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