passpadi

2002

Mathematics

JAMB

If the 9th term of an A.P is five times the 5th term, find the relationship between a and d.

A.

2a + 2 = 0

B.

3a + 5d = 0

C.

a + 3d = 0

D.

a + 2d = 0

Correct Answer: a + 3d = 0

Explanation

Tn = a + (n−1)d (nth term of an AP). T9=5T5 a + 8d = 5(a+4d) ⟹a + 8d = 5a + 20d 5a − a + 20d − 8d = 0 ⟹ 4a + 12d = 0 a + 3d = 0

Tn = a + (n−1)d (nth term of an AP). T9=5T5 a + 8d = 5(a+4d) ⟹a + 8d = 5a + 20d 5a − a + 20d − 8d = 0 ⟹ 4a + 12d = 0 a + 3d = 0
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