Tolong yg dlingkar yah^^ Pakai cara ya tlong..

17. 
[tex] \frac{3}{a + 1} - \frac{1}{a^{2}+a } = \frac{3a}{a (a + 1)} - \frac{1}{a(a+1)} = \frac{3a - 1}{a (a + 1)} [/tex]

19.
[tex] \frac{x+4}{x^{2}-9 } - \frac{2}{x+3} \\ \\ = \frac{x+4}{(x+3)(x-3)} - \frac{2 (x-3)}{(x+3)(x-3)} \\ \\ = \frac{x + 4 - 2x + 6}{ x^{2} -9} \\ \\ = \frac{-x+10}{ x^{2} -9} [/tex]