Question 101869
When adding or subtracing fractions, you need the same denominator. In this case you have that. Keep the same denominator and subtract the numerators. {{{4n^2/(2n+3) - 9/(2n+3)= (4n^2-9)/(2n+3)}}}. 
You can also reduce this by noticing that 
{{{(4n^2-9)= (2n+3)*(2n-3)}}}. 
Then you get
{{{RHS(Right Hand Side)=(2n+3)*(2n-3)/(2n+3)}}}. 
And finally
{{{RHS=(2n-3)}}}. 
The final answer : 
{{{4n^2/(2n+3) - 9/(2n+3)=(2n-3)}}}.