a)ĐKXĐ: \(\begin{matrix}x+3\ne0\\x-1\ne0\end{matrix}\)\(\left\{{}\begin{matrix}x\ne-3\\x\ne1\end{matrix}\right.\)
b)\(P=\dfrac{3x^2+5x-4}{\left(x+3\right)\left(x-1\right)}-\dfrac{x+1}{x+3}-\dfrac{x+3}{x-1}\)
\(P=\dfrac{3x^2+5x-4}{\left(x+3\right)\left(x-1\right)}-\dfrac{x^2-1}{\left(x+3\right)\left(x-1\right)}-\dfrac{\left(x+3\right)^2}{\left(x+3\right)\left(x-1\right)}\)
\(P=\dfrac{3x^2+5x-4-x^2+1-x^2-6x-9}{\left(x+3\right)\left(x-1\right)}\)
\(P=\dfrac{x^2-x-12}{\left(x+3\right)\left(x-1\right)}\)
\(P=\dfrac{\left(x+3\right)\left(x-4\right)}{\left(x+3\right)\left(x-1\right)}=\dfrac{x-4}{x-1}\)
Tại \(P=-\dfrac{1}{2}\) giá trị của x là:
\(\dfrac{x-4}{x-1}=-\dfrac{1}{2}\)
\(2x-8=1-x\)
\(3x=9\)
x=3
