if the 10th term of an AP is 1 and 28th term is -5 find the AP
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Answer:
AP : 4 , 11/3 , 10/3 , 3 , 8/3 , 7/3 ,...,
Step-by-step explanation:
a10= 1, a28 = -5
a10 = a + 9d
1. = a + 9d - eqn 1
a28 = a + 27d
-5 = a + 27d. - eqn 2
solving eqn 1 and 2
a +9d = 1
a + 27d = -5
(-). (-). (+)
_____________
- 18d = 6
d = 6/(-18)
d = -1/3
Substitute d= -1/3 in eqn 1
a + 9d = 1
a + 9 (-1/3) = 1
a + 3(-1) = 1
a - 3 = 1
a = 1+3
a = 4
Therefore the required AP is 4 , 11/3 , 10/3 , 3 , 8/3 , 7/3 , ......
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