a/
\(A=\dfrac{x+15}{\left(x-3\right)\left(x+3\right)}+\dfrac{2}{x+3}=\)
\(=\dfrac{x+15+2\left(x-3\right)}{\left(x-3\right)\left(x+3\right)}=\dfrac{3x+9}{\left(x-3\right)\left(x+3\right)}=\dfrac{3}{x-3}\)
b/
\(\dfrac{3}{x-3}=-\dfrac{1}{2}\Rightarrow x=x=-3\)
c/
Để A nguyên
\(\Rightarrow x-3=\left\{-3;-1;1;3\right\}\)
\(\Rightarrow x=\left\{0;-2;4;6\right\}\)