`#Sad`
`P= (3x^2+3x)/((x+1)(2x-6))`
`a,` `\text{ĐKXĐ:}`
`\(\left[ \begin{array}{l}x+1 \ne 0\\2x-6 \ne 0\end{array} \right.\)
`⇒` \(\left[ \begin{array}{l}x \ne -1\\x \ne 3\end{array} \right.\)
`b,`
`\text{·Rút gọn:}`
`P= (3x^2+3x)/((x+1)(2x-6))`
`P= (3x(x+1))/((x+1)(2x-6))`
`P= (3x)/(2x-6)`
`\text{·Để}` `P=1:`
`⇔ (3x)/(2x-6) = 1`
`⇔ 3x = 2x-6`
`⇔ 3x-2x = -6`
`⇔ x = -6`
`\text{Vậy để}` `P=1` `\text{thì}` `x=-6`
