Giải thích các bước giải:
$Bài$ $2:$
$a,- 59 - 9(2x - 1)² = - 140$
$→ 9(2x - 1)² = - 59 - (- 140)$
$→ 9(2x - 1)² = 81$
$→ (2x - 1)² = 81 : 9$
$→ (2x - 1)² = 9$
$→\left[ \begin{array}{l}2x - 1=3\\2x - 1 = - 3\end{array} \right.→\left[ \begin{array}{l}2x=4\\2x=- 2\end{array} \right.→\left[ \begin{array}{l}x=2\\x=-1\end{array} \right.$
$b, -2(-x - 5) + 28 = 20 - 3(x+ 4) $
$→ 2x + 10 + 28 = 20 - 3x - 12$
$→ 2x + 38 = - 3x + 8$
$→ 2x + 3x = 8 - 38$
$→ 5x = - 30$
$→ x = - 30 : 5$
$→ x= - 6$
$c, -7x + 11 = - 2x - 1$
$→ - 7x + 2x = - 1 - 11$
$→ - 5x = - 12$
$→ x = \frac{12}{5}$
