You can 
put this solution on YOUR website!    
Hi,
Re TY, Yes, you certainly had the right idea!

Yes. Consider when the denominator is zero
  3x^2 + x = 0
 x(3x+ 1) = 0   
 x = 0
Or (3x+ 1) = 0  
 x = 0  Or  x = -1/3  makes the denominator zero and make 4x/3x^2+x undefined