`e)`
`x^2 + 7 = 23`
`x^2 = 23 - 7`
`x^2 = 16`
`x^2 = 4^2`
`=> x = ±4`
`f)`
`x^2 + 8x = 3x + 24` `x^2 + 8x - ( 3x + 24 ) = 0`
`x^2 + 8x - 3x - 24 = 0`
`x(x + 8) - 3(x-3) = 0`
`(x + 8)(x-3) = 0`
$\Rightarrow\left[\begin{matrix} x+8=0\\ x-3=0\end{matrix}\right.$
$\Rightarrow\left[\begin{matrix} x= 0-8\\ x=0+3\end{matrix}\right.$
$\Rightarrow\left[\begin{matrix} x=-8\\ x=3\end{matrix}\right.$
`=>` Vậy `x = -8` hoặc `x=3`
`g)`
`x^3 - 49x = 0` `x(x^2 - 49x) = 0`
`x(x-7)(x+7) = 0`
$\Rightarrow\left[\begin{matrix} x= 0 \\ x-7=0\\ x+7=0\end{matrix}\right.$
$\Rightarrow\left[\begin{matrix} x=0 \\ x=0+7\\ x=0-7\end{matrix}\right.$
$\Rightarrow\left[\begin{matrix} x=0 \\ x=7\\ x=-7\end{matrix}\right.$
`=>` Vậy `x = 0` ;`x = 7` hoặc `x = -7`
`h)`
`36 .(4x+1)^2 = (3x+2)^2`
`[6(4x+1)]^2=(3x+2)^2`
`[6(4x+1)]^2-(3x+2)^2=0`
`[6(4x+1)+3x+2][6(4x+1)-(3x+2)]=0`
`(24x+6+3x+2)(24x+6-3x-2)=0`
`(27x+8)(21x+4)=0`
$\Rightarrow\left[\begin{matrix} 27x+8=0\\ 21x+4=0\end{matrix}\right.$
$\Rightarrow\left[\begin{matrix} 27x=0-8\\ 21x=0-4\end{matrix}\right.$
$\Rightarrow\left[\begin{matrix} 27x=-8\\ 21x=-4\end{matrix}\right.$
$\Rightarrow\left[\begin{matrix} x=-\dfrac{8}{27}\\ x=-\dfrac{-4}{21}\end{matrix}\right.$
`=>` Vậy `x= -8/27` hoặc `x=-4/21`
