How to find the vertical asymptote of a logarithmic function?

${\displaystyle f\left(x\right)={\log }_b\left(\text{argument}\right)}$ has vertical aymptotes at ${\displaystyle \text{argument}=0}$
Example ${\displaystyle f\left(x\right)=\ln (x^2-3x-4).}$ has asymptotes in the vertical
${\displaystyle x=4}$ and ${\displaystyle x=-1}$
graph{y=ln(x^2-3x-4) [-5.18, 8.87, -4.09, 2.934]}
Example ${\displaystyle f\left(x\right)=\ln \left(\frac{1}{x}\right)}$ has vertical asymptote
${\displaystyle x=0}$
graph{ln(1/x) [-5.18, 8.87, -4.09, 2.934]}
Example ${\displaystyle f\left(x\right)=\ln \left(\frac{1}{x^2}\right)}$ alsohas vertical asymptote
${\displaystyle x=0}$
graph{ln(1/x^2) [-5.18, 8.87, -4.09, 2.934]}