Question

algebric form of an arithmetic sequence is 5n + 4. find the sum of the first 20 terms​

Answer 1

༒࿐៚ Answer ༒࿐៚

Firstly, we have to find its 10th and 20th term.

For this, we have a_{1} a

1

= 9

\underline{\tt{For \:n\: = \:10}}

Forn=10

,

5n + 4 = 5( 10 ) + 4 = 54

a_{10} a

10

= 54

\fbox{a_{10} \:=\: 54}

Now, \underline {\tt{For \:n\: =\: 20}}

Forn=20

a_{20} a

20

= 5 ( 20 ) + 4 = 104

\fbox{a_{20} \:=\: 104}.