a)
[tex]8x^2-3x=0\\x(8x-3)=0\\x=0\vee8x-3=0\\x=0\vee8x=3\ |:8\\x=0\vee x=\frac{3}{8}[/tex]
b)
[tex]7x^2=21x\\7x^2-21x=0\ |:7\\x^2-3x=0\\x(x-3)=0\\x=0\vee x-3=0\\x=0\vee x=3[/tex]
c)
[tex]x(x+2)=4x(x+2)\\x(x+2)-4x(x+2)=0\\(x+2)(x-4x)=0\\(x+2)(-3x)=0\\-3x(x+2)=0\ |:(-3)\\x(x+2)=0\\x=0\vee x+2=0\\x=0\vee x=-2[/tex]
