Question

find the sum of all positive terms of AP 312+307+302.....................so on​

Answer 1

Answer: n/2(629-5n).

Explanation:

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

Here, a= 312 and d= -5

then, put the values of a and d.

Sn= n/2(2*312+(n-1)(-5))

Sn= n/2(624-5n+5)

Sn= n/2(629-5n).