Bài 2: Tìm các số nguyên x, biết: d) ( -x + 5 ) x ( 3 - x ) =0 e) x + 5 = 20 - ( 12 - 7 ) f) 15 - ( 3 + 2x ) = 2 mũ 2

$2)$. 

$d) ( -x - 5 )$ `xx` $( 3 - x ) = 0$

$\Rightarrow$ $\left[\begin{matrix} 5-x=0\\ 3-x=0\end{matrix}\right.$

$\Rightarrow$ $\left[\begin{matrix} x=5-0\\ x=3-0\end{matrix}\right.$

$\Longrightarrow$ $\left[\begin{matrix} x=5\\ x=3\end{matrix}\right.$

Vậy $x$ $\in$ `{$5 ; 3$}`

$----------------$

e) $x + 5 = 20 - ( 12 - 7 )$

$\Rightarrow$ $x + 5 = 20 - 5$

$\Rightarrow$ $x + 5 = 15$ 

$\Rightarrow$ $x = 15 - 5$ 

$\Longrightarrow$ $x = 10$ 

Vậy $x = 10$

$-------------------$

$f) 15 - ( 3 + 2x ) = 2^2$

$15 - ( 3 + 2x ) = 4$

$3 + 2x = 15 - 4$

$3 + 2x = 11$

$2x = 11 - 3$

$2x = 8$

$x = 4$