Question

In an A.P. a=1,d=1 Sn=19800 find n​

Answer 1

Step-by-step explanation:

• use Formula Sn=n/2[2a+(n-1)d]
• use Formula Sn=n/2[2a+(n-1)d]and Put values of a,d and Sn and you will get the answer.

Hope you understood this.

Thanks.

Answer 2

sn= n/2(2a+(n-1).d

19800=n/2(2+(n-1).1

19800=n/2(2-1+n)

19800=n/2*1+n

19800=n+n²/2

19800*2=n+n²

39600=n+n²

This is answer of this question

I hope this will help you