Đáp án:
Giải thích các bước giải:
a) $2x(x-5)+7(x-3)=0$
$2x² - 10x + 7x - 21 = 0$
$2x² - 3x - 21 = 0$
$(x - \dfrac{3 + \sqrt{177}}{4})(x - \dfrac{3 - \sqrt{177}}{4}) = 0$
\(\left[ \begin{array}{l}x=\dfrac{3 + \sqrt{177}}{4}\\x=\dfrac{3 - \sqrt{177}}{4}\end{array} \right.\)
b) $4x² - 12x + 5 = 0$
$4x² - 2x - 10x + 5 = 0$
$( 2x - 5)(2x - 1) = 0$
\(\left[ \begin{array}{l}2x - 5=0\\2x - 1=0\end{array} \right.\)
\(\left[ \begin{array}{l}x=\dfrac{5}{2}\\x=\dfrac{1}{2}\end{array} \right.\)
