Question

27) If sum of n terms of an A.P. is n2+13, find its 13th term.​

Answer 1

Answer:

Step-by-step explanation:

⇒S  

1

​

=2(1)+3(1)  

2

=5

S  

n

​

=  

2

n

​

{2a+(n−1)d}

S  

n

​

=  

2

n

​

{a+a+(n−1)d}

S  

n

​

=  

2

n

​

{a+a  

n

​

}

2n+3n  

2

=  

2

n

​

{5+a  

n

​

}

4+6n=5+a  

n

​

 

⇒a  

n

​

=6n−1

⇒a  

r

​

=6r−1

Answer 2

Answer:

15 is the sum

Step-by-step explanation:

$2 + 13 = 15 \: 27 - 15 = 12$

12-15= -3