a) 4x² - 3(2x - 5) - 25 = 0
⇔ 4x² - 6x + 15 - 25 = 0
⇔ 4x² - 6x - 10 = 0
⇔ 4x² + 4x - 10x - 10 = 0
⇔ 2x² + 2x - 5x - 5 = 0
⇔ 2x( x + 1 ) - 5( x + 1 ) = 0
⇔ ( x + 1 )( 2x - 5 ) = 0
⇔ \(\left[ \begin{array}{l}x+1=0\\2x-5=0\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=-1\\x=\frac{5}{2} \end{array} \right.\)
b) (3x - 2)² - ( x - 1)(3x - 5) = 6x² - 7
⇔ 9x² - 12x + 4 - ( 3x² - 5x - 3x + 5 ) - 6x² + 7 = 0
⇔ 3x² - 12x + 11 - 3x² + 5x + 3x - 5 = 0
⇔ -4x + 6 = 0
⇔ -4x = -6
⇔ x = $\frac{6}{4}$
⇔ x = $\frac{3}{2}$
~CHÚC BẠN HỌC TỐT~
