Question

The sum of the first 7 terms of an AP is 49 and that of the first 17 terms is 289.
What is the sum of the first n terms

Answer 1

this is ur answer for the question

Answer 2

Hey !!! ^_^

here is your answer

⬇️⬇️⬇️⬇️⬇️⬇️⬇️⬇️

In attachment ...☺️


Here ...

The sum first 7th term is 49 and the sum of 17th term is 289 ...

So ..

S7 = 49

and

S17 = 289 ...



using the formula of

Sn = n/2[2a + (n - 1)d]

u got the equation ..

a + 8d = 1 7

and

a + 3d = 7 ...

Solve this equation by elimination Process.....

u got the ans

D = 2..


and

a = 1..


Again use .

The sum of term of Ap formula ...


U got the ans ...

Sn = n^2 ..


======================

I HOPE IT WILL HELP YOU

Thank you

☺️