$\text{Bài tập 1:}$
$\text{$x^2$ - $y^2$ + 12y - 36.}$
$\text{= $x^2$ - ($y^2$ - 12y + 36).}$
$\text{= $x^2$ - ($y^2$ - 2.y.6 + $6^2$).}$
$\text{= $x^2$ - $(y - 6)^2$.}$
$\text{= [x + (y - 6)].[x - (y - 6)].}$
$\text{= (x + y - 6).(x - y + 6).}$
$\text{Bài tập 2:}$
$\text{$8x^3$ - 50x = 0.}$
$\text{⇒ 2x.($4x^2$ - 25) = 0.}$
$\text{⇒ 2x.[$(2x)^2$ - $5^2$] = 0.}$
$\text{⇒ 2x.(2x + 5).(2x - 5) = 0.}$
$\text{⇒ \(\left[ \begin{array}{l}2x=0.\\2x+5=0.\\2x - 5 = 0.\end{array} \right.\)}$
$\text{⇒ \(\left[ \begin{array}{l}x=0.\\2x=-5.\\2x = 5.\end{array} \right.\)}$
$\text{⇒ \(\left[ \begin{array}{l}x=0.\\x=\dfrac{-5}{2}.\\x = \dfrac{5}{2}.\end{array} \right.\)}$
$\text{Vậy x = 0; x = $\dfrac{-5}{2}$ hoặc x = $\dfrac{5}{2}$.}$
