Question 258868
Look for values of x that are not allowed or lead to an undefined function. 
Particularly, division by zero, square root and logarithm arguments less than zero. 
Examples:
{{{f(x)=5/(x-2)}}}, {{{x=2}}} is not allowed, because of division by zero.
{{{ graph( 300, 300, -5, 5, -10, 10, 5/(x-2)) }}}
.
.
.
{{{g(x)=(x-2)/sqrt(3-x)}}}, {{{x>=3}}} is not allowed. 
{{{ graph( 300, 300, -5, 5, -10, 10, (x-2)/sqrt(3-x)) }}}
.
.
.
etc.