5x2 - 26x - 24 = 0
⇔ 5x2 - 30x + 4x - 24 = 0
⇔ 5x( x - 6 ) + 4( x - 6 ) = 0
⇔ ( x - 6 )( 5x + 4 ) = 0
⇔ x - 6 = 0 hoặc 5x + 4 = 0
⇔ x = 6 hoặc x = -4/5
Trả lời :
5x2 - 26x - 24 = 0
=> 5x . (x - 6) + 4x - 24 = 0
=> 5x . (x - 6) + 4 . (x - 6) = 0
=> (5x + 4) . (x - 6) = 0
\(\Rightarrow\orbr{\begin{cases}5x+4=0\\x-6=0\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=\frac{-4}{5}\\x=6\end{cases}}\)