(2a+1) for any value of a The answer is odd number
(9a+4) for any value of a The answer is odd number or even number
2a+1<9a+1
If,a=0
then,(2a+1,9a+4)=1(gcd).
If,a=1,2,3,4,5,6,7,8,9
then also (2a+1,9a+4)=1(gcd)
By maintaining this agrument For any valve upto 9 from 0 the ans is 1
Since,Both number cant be divisibe by 2,3,4,5,6,7,8,9; Then only G.C.D that left can be conclude from Previous result is 1
Since,(2a+1,9a+4)=1(gcd) <hence proved> For,Real +whole numbers