This means that when x→ 1, the limit of f(x)/(x- 1) exists.

And when the molecule x- 1 is x→ 1, x- 1=0.

Then, the limit of the original fraction f(x)/(x- 1) must be guaranteed.

F(x)=0 is only possible when x→ 1.

X- 1 This is a 0 when X approaches 1, so the molecule f(x) must also be a number approaching 0 to satisfy this limit formula, so we can get that f( 1)=0.