Tìm x:
a)2x²+5x=0
⇔x.(2x+5)=0
⇔$\left \{ {{x=0} \atop {2x+5=0}} \right.$
⇔$\left \{ {{x=0} \atop {2x=-5}} \right.$
⇔$\left \{ {{x=0} \atop {x= \frac{-5}{2}}} \right.$
Vậy x=0 hoặc x=$\frac{-5}{2}$
b)4x²-25=0
⇔(2x)²-5²=0
⇔(2x-5).(2x+5)=0
⇔$\left \{ {{2x-5=0} \atop {2x+5=0}} \right.$
⇔$\left \{ {{2x=5} \atop {2x=-5}} \right.$
⇔$\left \{ {{x=\frac{5}{2}} \atop {x=\frac{-5}{2}}} \right.$
Vậy x=$\frac{5}{2}$ hoặc x=$\frac{-5}{2}$
c)x³-2x²=0
⇔x².(x-2)=0
⇔$\left \{ {{x²=0} \atop {x-2=0}} \right.$
⇔$\left \{ {{x=0=2} \atop {x=2}} \right.$
Vậy x=0 hoặc x=2
~ chúc tus học tốt nha!!!~
