The sum of first 8 term of an ap is 100 and sum of first 19 terms is 551 find ap
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Answer:
4, 7, 10, 13, 16...……
Step-by-step explanation:
S8 = 4[2a + (n-1)d]
100 = 4 [2a + 7d]
25 = 2a + 7d -----------(1)
S19 = 19/2 [ 2a + 18d]
1102 = 19 [2a + 18d]
58 = 2a + 18d -------------------(2)
Eqn2 - Eqn1
58 = 2a +18d
25 = 2a + 7d
----------------------------
33 = 11d
d = 3
25 = 2a + 7(3)
25 = 2a + 21
2a = 4
a = 4
The AP is 4, 7, 10, 13, 16...……
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