a, ĐKXĐ: \(\left[{}\begin{matrix}x+1\ne0\\2x-6\ne0\end{matrix}\right.< =>\left[{}\begin{matrix}x\ne-1\\x\ne3\end{matrix}\right.\)
b, Khi P bằng 1:
\(P=1\\ < =>\dfrac{3x^2+3x}{\left(x+1\right)\left(2x-6\right)}=1\\ < =>\dfrac{3x\left(x+1\right)}{\left(x+1\right)2\left(x-3\right)}=1\\ < =>\dfrac{3x}{2\left(x-2\right)}=1\\ =>3x=2\left(x-2\right)\\ < =>3x=2x-4\\ < =>3x-2x=-4\\ < =>x=-4\)
Vậy; Để P=1 thì x= -4