Question

If the nth term of an AP is 3+4n then find the sum of the first 15th terms

Answer 1

Answer

3+4n

Putting value of n as 1

3+4×1=7

Now putting value of n as 2

3+4×2=11

So,ap=7,11,15,19.......

Sn=n/2{2a +n-1+×d}

S15=15/2{14 +14×4}

S15=15/2×70

S15=15×35

S15=525

Answer 2

Answer:

525

Step-by-step explanation:

Putting value of n as 1

3+4x1=7

Now putting value of n as 2

3+4x2=11

so,AP =7,11,15,19

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

S15=15/2(14+14x4)

S15=15/2x70

S15=15x35

S15=525

Hope this answer is helpful!!!