Question

What is the sum of the first 36 terms of an A.P., whose nth term is 4n + 5?

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Answer 1

Answer:

2844

Step-by-step explanation:

solution given in image

Answer 2

Answer:

Hence, the sum of first 30 terms is 1020

Step-by-step explanation:

It is given that the nth term of A.P is T

n=3+2n.

We know that the general term of an arithmetic progression with first term a

and common difference d is Tn =a+(n−1)d, therefore,

Tn=3+2n=5+(n−1)2

Comparing the above term by the general term of A.P, we get a=5 and d=2

We also know that the sum of an arithmetic series with first term a and common

difference d is Sn= 2n [2a+(n−1)d] as follows:

S30= 2 30 [(2×5)+(30−1)2]=15[10+(29×2)]=15(10+58)=15×68=1020