The question is:
Solve for $x$ in the following
$\log_{10}{(x^2-12x+36)}=2$
Now, solving for $x$, we get;
$(x-6)^2=100$
$\implies x=-4 $or $x=16$
But, these are the roots of that equation. So, if I put the value of $x$ in the original equation to check, I get;
$\log{0}=100$ which can not be true.
SO, why are we counting both the roots as solutions?
Assuming you're trying to solve $$\log (x^2-12x+36)=2$$ And the $\log$ is base $10$, I'm not sure how you get $\log 0=100$. If you put both $-4, 16$ back in, we get $$\log 100=2$$ As expected.