Find the nth term Un of the A.P., 11, 4, -3,....... .
A
Un=19+7n
B
Un=19-7n
C
Un=18+7n
D
Un= 18-7n
E
Un= 17-7n
Verified Correct Answer: D.
Step-by-Step Mathematical Solution
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
Source: Myschool Past Questions Archive (Record #23693)