Question

the sum of the first 7 terms of an ap is 140 and the sum of the next 7 terms of the sum progression is 385 then find the AP​

Answer 1

Answer:

S7 = 140 & S14 - S7 = 385

» S7 = 140

2a + 6d = 40 ... (1)

» S14 - S7 = 385

7 (2a + 13d) - 140 = 385

» 7 (2a + 13d) = 525

» 2a + 13d = 75 ... (2)

On solving (1) & (2), we get

Therefore, a = 5 & d = 5

Therefore, the required A.P. is a, a + d, a + 2d, ...

» Therefore, the required A.P. is

5, 10, 15, ..., 5 + (n - 1)d

Answer 2

Step-by-step explanation:

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