Đáp án+giải thích các bước giải:
a)
$4x^2-25+(5-2x).(2x+7)=0$
$4x^2-25+10x+35-4x^2-14x=0$
$10-4x=0$
$2(5-2x)=0$
$x=\dfrac{5}{2}$
Vậy $x=\dfrac{5}{2}$
b)
$3x^2-5x+2=0$
$3x^2-3x-2x+2=0$
$(3x^2-3x)-(2x-2)=0$
$3x(x-1)-2(x-1)=0$
$(x-1)(3x-2)=0$
$⇒$\(\left[ \begin{array}{l}x-1=0\\3x-2=0\end{array} \right.\)
$⇒$\(\left[ \begin{array}{l}x=1\\x=\dfrac{2}{3}\end{array} \right.\)
Vậy \(\left[ \begin{array}{l}x=1\\x=\dfrac{2}{3}\end{array} \right.\)
