For the specific problem you do not even have to perform the long division.
Notice that ( 4x +3 ) / (2 x+ 1 ) = ( 4x +2 +1 ) / (2 x+ 1 ) = [ 2( 2 x+ 1 ) +1 ] / (2 x+ 1 )
= 2( 2 x+ 1 ) / (2 x+ 1 ) + 1 / (2 x+ 1 ) = 2 + (1/2) [ 1 /( x +1 /2) .
Now the ball is in your court