Question

in an ap the first term is 22 ,nth term is -11 and sum to first n terms is 66 find n and d , the common difference

Answer 1

Given, a = 22 , an = -11 , Sn = 66
So, an = a + (n-1)d
=>-11 = 22 + (n-1)d
=> (n-1)d = -33. .............(i)

Now, Sn = 66
=> n/2(a + an) = 66
=> n/2 (22-11) = 66
=> n/2 = 66/11
=> n = 12. ................(ii)

Putting (ii) in (i).....
=> d(n-1) = -33
=> d(12-1) = -33
=> d = -33/11
=> d = -3

Answer 2

Answer:

Step-by-step explanation: