\(a,ĐKXĐ:\\ \left[{}\begin{matrix}x+1\ne0\\2x-6\ne0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x\ne-1\\x\ne3\end{matrix}\right.\\ b,P=0\\ \Leftrightarrow\dfrac{3x^2+3x}{\left(x+1\right)\left(2x-6\right)}=0\\ \Leftrightarrow\dfrac{3x\left(x+1\right)}{3\left(x+1\right)\left(x-2\right)}=0\\ \Leftrightarrow\dfrac{x}{x-2}=0\\ \Leftrightarrow x=0\left(TM\right)\)

Vậy tại X=0 thì P=0

a) Để P xác định thì: \(\left[{}\begin{matrix}x+1\ne0\\2x-6\ne0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x\ne-1\\x\ne3\end{matrix}\right.\)

b) \(P=\dfrac{3x^2+3x}{\left(x+1\right)\left(2x-6\right)}=\dfrac{3x\left(x+1\right)}{\left(x+1\right)\left(2x-6\right)}=\dfrac{3x}{2x-6}\)

Để \(P=0\) thì: \(\dfrac{3x}{2x-6}=0\)

\(\Leftrightarrow3x=0\)

\(\Leftrightarrow x=0\left(tm\right)\)

a,ĐK:  \(\hept{\begin{cases}x\ne0\\x\ne\pm3\end{cases}}\)

b, \(A=\left(\frac{9}{x\left(x-3\right)\left(x+3\right)}+\frac{1}{x+3}\right):\left(\frac{x-3}{x\left(x+3\right)}-\frac{x}{3\left(x+3\right)}\right)\)

\(=\frac{9+x\left(x-3\right)}{x\left(x-3\right)\left(x+3\right)}:\frac{3\left(x-3\right)-x^2}{3x\left(x+3\right)}\)

\(=\frac{x^2-3x+9}{x\left(x-3\right)\left(x+3\right)}.\frac{3x\left(x+3\right)}{-x^2+3x-9}=\frac{-3}{x-3}\)

c, Với x = 4 thỏa mãn ĐKXĐ thì

\(A=\frac{-3}{4-3}=-3\)

d, \(A\in Z\Rightarrow-3⋮\left(x-3\right)\)

\(\Rightarrow x-3\inƯ\left(-3\right)=\left\{-3;-1;1;3\right\}\Rightarrow x\in\left\{0;2;4;6\right\}\)

Mà \(x\ne0\Rightarrow x\in\left\{2;4;6\right\}\)

a, ĐKXĐ: \(\hept{\begin{cases}x^3+1\ne0\\x^9+x^7-3x^2-3\ne0\\x^2+1\ne0\end{cases}}\)

b, \(Q=\left[\left(x^4-x+\frac{x-3}{x^3+1}\right).\frac{\left(x^3-2x^2+2x-1\right)\left(x+1\right)}{x^9+x^7-3x^2-3}+1-\frac{2\left(x+6\right)}{x^2+1}\right]\)

\(Q=\left[\frac{\left(x^3+1\right)\left(x^4-x\right)+x-3}{\left(x+1\right)\left(x^2-x+1\right)}.\frac{\left(x-1\right)\left(x+1\right)\left(x^2-x+1\right)}{\left(x^7-3\right)\left(x^2+1\right)}+1-\frac{2\left(x+6\right)}{x^2+1}\right]\)

\(Q=\left[\left(x^7-3\right).\frac{\left(x-1\right)}{\left(x^7-3\right)\left(x^2+1\right)}+1-\frac{2\left(x+6\right)}{x^2+1}\right]\)

\(Q=\frac{x-1+x^2+1-2x-12}{x^2+1}\)

\(Q=\frac{\left(x-4\right)\left(x+3\right)}{x^2+1}\)

a)\(\hept{\begin{cases}x+1\ne0\\2x-6\ne0\end{cases}\Leftrightarrow}\hept{\begin{cases}x\ne-1\\x\ne3\end{cases}}\)

b)\(\frac{3x^2+3x}{\left(x+1\right)\left(2x-6\right)}=10\)\(\Leftrightarrow\frac{3x\left(x+1\right)}{\left(x+1\right)\left(2x-6\right)}=10\)

\(\Leftrightarrow\frac{3x}{2x-6}=10\)\(\Leftrightarrow3x=10\left(2x-6\right)\)

\(\Leftrightarrow3x=20x-60\)\(\Leftrightarrow17x=60\Leftrightarrow x=\frac{60}{17}\)

a, \(x\ne-1;3\)

b, Ta có : \(P=\frac{3x^2+3x}{\left(x+1\right)\left(2x-6\right)}=1\)

\(\Leftrightarrow\frac{3x\left(x+1\right)}{\left(x+1\right)\left(2x-6\right)}=1\Leftrightarrow\frac{3x}{2\left(x-3\right)}=1\)

\(\Leftrightarrow3x=2x-6\Leftrightarrow x=-6\)

\(a,x\ne2;x\ne-2;x\ne0\)

\(b,A=\left(\frac{x}{x^2-4}+\frac{2}{2-x}+\frac{1}{x+2}\right):\frac{6}{x+2}\)

\(=\frac{x-2\left(x+2\right)+x-2}{\left(x-2\right)\left(x+2\right)}:\frac{6}{x+2}\)

\(=\frac{-6}{\left(x-2\right)\left(x+2\right)}:\frac{6}{x+2}\)

\(=\frac{-6}{\left(x-2\right)\left(x+2\right)}.\frac{x+2}{6}\)

\(=\frac{1}{2-x}\)

\(c,\)Để A > 0 thi \(\frac{1}{2-x}>0\Leftrightarrow2-x>0\Leftrightarrow x< 2\)