Đáp án:
$S =${$3;\frac{-11}{10}$}
Giải thích các bước giải:
$(8x - 3)(3x + 2) - (4x + 7)(x + 4) = (2x + 1)(5x - 1)$
$→ 24x² + 16x - 9x - 6 - (4x² + 16x + 7x + 28) = 10x² + 5x - 2x - 1$
$→ 24x² + 7x - 6 - (4x² + 23x + 28)=10x² + 3x - 1$
$→ 24x² + 7x - 6 - 4x² - 23x - 28 = 10x² + 3x - 1$
$→ 20x² - 16x - 34 = 10x² + 3x - 1$
$→ 10x² - 19x - 33 = 0$
$→ (10x² + 11x) - (30x + 33) = 0$
$→ x(10x + 11) - 3(10x + 11) = 0$
$→ (x - 3)(10x + 11) = 0$
$→\left[ \begin{array}{l}x- 3 = 0\\10x + 11=0\end{array} \right.$
$→\left[ \begin{array}{l}x=3\\x=\frac{-11}{10}\end{array} \right.$
Vậy $S =${$3;\frac{-11}{10}$}
