WAEC - Mathematics (1995 - No. 6)
Find the nth term Un of the A.P., 11, 4, -3,....... .
Un=19+7n
Un=19-7n
Un=18+7n
Un= 18-7n
Un= 17-7n
Explanation
A.P 11, 4, -3
1st term = 11
A.P = a, a + d, a + 2d ...... a + (n - 1)d
If a = 11
a + d = 4
d = 4 - 11 = -7
nth term = a + (n-1)d
= 11 + (n-1)(-7)
= 11 - 7n + 7
= 18 - 7n
1st term = 11
A.P = a, a + d, a + 2d ...... a + (n - 1)d
If a = 11
a + d = 4
d = 4 - 11 = -7
nth term = a + (n-1)d
= 11 + (n-1)(-7)
= 11 - 7n + 7
= 18 - 7n
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