Question

gys plz.....answer this question this is too important because my pre board are held on 3 dec .
The sum of first 9 terms of an A.Pis 351 and the sum of its first 20 terms is 1770 . find the first term and the common difference of the A.P.

Answer 1

Answer: a = -681

              d = 129

Step-by-step explanation:

a+8d = 9th term.

a+8d = 351. ---------(1)

a+19d = 1770--------(2)

subtracting both,

a+8d = 351

a+19d = 1770

-------------------

-11d = -1419

d = 129

a+8d = 351

a+8 * 129 = 351

a = -681.

Hope it helps