3x2+9x=0 --> 3x(x+3)=0 --> 3x=0 hoặc x+3=0
--> x=0 hoặc x =-3
\(\dfrac{1}{4}\)x2-\(\dfrac{1}{2}\)x=0-->\(\dfrac{1}{2}\)x(\(\dfrac{1}{2}\)x-1)=0--> x=o hoặc x=2
32x2+24x=0-->8x(4x+3)=0 --> x=0 hoặc x=-3/4
25x2-15x=0 -->5x(5x-3)=0 --> x=0 hoặc x=3/5