Question

The nth term of an arithmetic sequence is a,-5 -6n. Find its

sum of n terms?​

Answer 1

Step-by-step explanation:

Given: an = 5-6n

Find some of the terms of AP:

Put n= 1, we get a1 = -1 = first term

Put n =2, we get a2 = -7 = second term

Common Difference = d = a2-a1 = -7-(-1) = -6

Sum of First n terms:

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

= n/2[-2+(n-1)(-6)]

= n(2-3n)