The first three terms of an AP respectively are $3y-1,\ 3y\ +5$ and $5y\ +1$.
Then y equals:
$( A) -3\ $
$ ( 8) \ 4$
$ ( C) \ 5$
$( D) \ 2$


Given: first three term of the A.P. $\displaystyle 3y-1,\ 3y+5\ and\ 5y+1\ $

To do: To find the value of y.

Solution:

The first three terms of an AP are$\displaystyle \ 3y-1,\ 3y+5\ and\ 5y+1$, respectively. 

We need to find the value of y. 

We know that if a, b and c are in AP, 

Then $b-a=c-b$

$2b=a+c$

$2( 3y+5)=3y-1+5y+1$

$6y+10=8y$

$8y-6y=10$

$2y=10$

$y=\frac{10}{2}$

$y=5$

Hence, The correct option is $( C)$ .

Updated on: 10-Oct-2022

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