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WAEC 2025 · Paper 1 · Q7✱✱

Find the nnth term UnU_n of the arithmetic progression 11,4,−3,…11, 4, -3, \dots

Worked solution (try it first)
  1. This is an A.P. with a=11a = 11 and d=4−11=−7d = 4 - 11 = -7.
  2. So Un=a+(n−1)d=11−7(n−1)U_n = a + (n - 1)d = 11 - 7(n - 1).
  3. Expand: 11−7n+7=18−7n11 - 7n + 7 = 18 - 7n, option C.

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