Question

Find the sum of first 25 terms of an ap whose nth term is 7-4n

Answer 1

प्रथम 25 पदों का योग = n/2 {a + a(n)}

{चूंकि a(n) = 7 - 4n}

= n/2 {a + 7 - 4n}

= 25/2 {a + 7 - 100}

= 25/2{a - 93}