Bạn tham khảo:
a/ $( 7 - x ) - ( 13 + x ) = 0$
$⇔ 7 - x - 13 - x = 0 $
$⇔ -x - x = -7 + 13$
$⇔ ( -1 - 1 ).x = 6$
$⇔ -2x = 6$
$⇔ x = 6 : ( -2 )$
$⇔ x = -3$
b/ $-9[ x + ( -2 ) ] = 0 $
$⇔ -9x + (-9 ) . ( -2 ) = 0$
$⇔ -9x + 18 = 0 $
$⇔ -9x = -18 $
$⇔ x = ( - 18 ) : ( -9 )$
$⇔ x = 2$
c/ $x + 2x + x + 91 = -5$
$⇔ ( 1 + 2 + 1 ).x = -5 - 91$
$⇔ 4x = -96 $
$⇔ x = -24$
d/ $-125 - ( 3x + 1 ) = ( -2 ). ( -27 )$
$⇔ -125 - 3x - 1 = 54$
$⇔ -3x = 54 + 125 + 1$
$⇔ -3x = 180 $
$⇔ x = 180 : ( - 3 )$
$⇔ x = -60 $
e/ $5.( -4 ).x = 100$
$⇔ -20x = 100 $
$⇔ x = 100 : ( - 20 )$
$⇔ x = -5$
f/ $x^{2} - 7x = 0$
$⇔ x.x - 7x = 0 $
$⇔ x( x - 7 ) = 0 $
$⇔$ \(\left[ \begin{array}{l}x=0\\x-7=0\end{array} \right.\)
$⇔$ \(\left[ \begin{array}{l}x=0\\x=7\end{array} \right.\)
