Question

if 5 term of an ap is -13 and the sum of the first four terms is 24 what is the sum of first n term​

Answer 1

Step-by-step explanation:

d= common difference

a=1st term

Let n be 5

Now, a+(5-1)d

a+4d= -13................................(i)

Let n be 4

4/2(2a+3d)=24

2a+3d=12...............................(ii)

Now, (i) can be written as 2a+8d=-26

Subtract (i) and (ii)

We will get 5d=-38

d=-38÷5

Substitute d in (i)

We will get a =87/5

We have to find the nth term

87/5+(n-1)-38/5

87/5+-38/5n+38/5

25-38/5 n