X2 - 4x = x(x - 4)
The only factor of x2 is x.
The factors of 4x are 4 and x.
The only common factor of the two terms is x. When this is extracted from both terms it leaves the remaining factor for the original expression, namely x - 4.
The only factor of x2 is x.
The factors of 4x are 4 and x.
The only common factor of the two terms is x. When this is extracted from both terms it leaves the remaining factor for the original expression, namely x - 4.