1.
(x-3)=x(x-3)
(x-3)-x(x-3)=0
(x-3)(1-x)=0
x=3或x=1
2.
5x^2=4x
5x^2-4x=0
x(5x-4)=0
x=0或x=4/5
3.
(x-2)^2=(2x+3)^2
(x-2)^2-(2x+3)^2=0
(x-2+2x+3)(x-2-2x-3)=0
(3x+1)(-x-5)=0
3x=1或x+5=0
x=-1/3或x=-5
4.
x^3-16x=0
x(x^2-16)=0
x(x+4)(x-4)=0
x=0或x=-4或x=4