what does this pair with 6/sqrt(21=? does it equal out to this 2*sqrt(21/7?

6 / √21      multiply top/bottom by √21

[ 6 √21 ] / [√21 √21 ]  =

[6 √21 ] / 21   =

(6/21) √21 =

(2/7) √ 21  =

 [ 2 √ 21 ] / 7