a) Giá trị của biểu thức A đc xđ khi:\(\left\{{}\begin{matrix}x+3\ne0\\x^2+x-6\ne0\\2-x\ne0\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}x\ne-3\\x\ne2\end{matrix}\right.\)
Vây đkxđ là \(\left\{{}\begin{matrix}x\ne-3\\x\ne2\end{matrix}\right.\)
P=\(\frac{x+2}{x+3}-\frac{5}{x^2+x-6}+\frac{1}{2-x}\)
=\(\frac{\left(x+2\right)\left(x-2\right)}{\left(x+3\right)\left(x-2\right)}-\frac{2}{\left(x+3\right)\left(x-2\right)}-\frac{x+3}{\left(x+3\right)\left(x-2\right)}\)
=\(\frac{x^2-4-2-x-3}{\left(x+3\right)\left(x-2\right)}\)
=\(\frac{x^2-x-9}{\left(x+3\right)\left(x-2\right)}\)