Question

The sum of the first terms of an arithmetic sequence is Sn=bn-2n2. Find b if the tenth term is -16.

Answer 1

Answer:

Correct option is

B

120

The sum of n terms of arithmetic sequence can be calculated by the formula  

S  

n

​  

=  

2

n

​  

(a  

1

​  

+a  

n

​  

)Sn=n2(a1+an)

is the first term and the last term.n=10

First term =2

Tenth term =22

∴S  

n

​  

=  

2

10

​  

(22+2)

∴S  

n

​  

=10(12)=120

Step-by-step explanation: