1)x^2-7x=0 5)8x^3-50x=0
<=>x(x-7)=0 <=>2x(4x^2-25)=0
<=>x=0hoac x-7=0 <=>2x=0 hoac 4x^2-25=0
<=>x=0hoacx=7 <=>x=0 hoac 4x^2=25
vay x=0 hoac x=7 <=>x=0 hoac x^2=25/4
2)x+5x^2=0 <=>x=0 hoac x=5/2
<=>x(1+5x)=0 9)5x(x-1)-3(x-1)=0
<=>x=0 hoac 1+5x=0 <=>(x-1)(5x-3)=0
<=>x=0 hoac 5x=-1 <=>x-1=0 hoac 5x-3=0
<=>x=0 hoac x=-1/5 <=>x=1 hoac 5x=3
4)-3x+5x=0 <=> x=1 hoac x=3/5
<=>x(-3+5)=0
<=>2x=0
<=>x=0
vay x=0
