JAMB 2000 · UME · Q13

The 3rd term of an A.P. is 4x−2y4x - 2y and the 9th term is 10x−8y10x - 8y. Find the common difference.

Worked solution (try it first)
  1. From the 3rd term to the 9th term is 6 steps of dd: (a+8d)−(a+2d)=6d(a + 8d) - (a + 2d) = 6d.
  2. Subtract the terms: (10x−8y)−(4x−2y)=6x−6y(10x - 8y) - (4x - 2y) = 6x - 6y.
  3. So 6d=6x−6y6d = 6x - 6y and d=x−yd = x - y, option C.

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