Question 1008965
Any line perpendicular to the x-axis will
have an equation that looks like:
{{{ x = a }}} where the {{{ a }}} is given by
any of the points that the line passes through. 
All these points look like: ( a, y ), where {{{ y }}}
can be any value.
You are given the point ( 4,1 ), so {{{ a = 4 }}}
and the equation of the line is:
{{{ x = 4 }}}