Question 1121609
yes, {{{y=8}}} {{{is}}} a function

{{{y=8}}} means:

{{{x}}}|{{{y}}}
{{{1}}}|{{{8}}}
{{{2}}}|{{{8}}}
{{{3}}}|{{{8}}}
{{{4}}}|{{{8}}}
:
etc

so, you are given horizontal line:

{{{ graph( 600, 600, -10, 10, -10, 10, 8,8) }}}


since you are given a straight horizontal line, use this way of determining if an equation is using the {{{vertical}}}{{{ line}}} {{{test}}}. In mathematics, the vertical line test is a test to determine if a relation or its graph is a function or not. For a relation or graph to be a function, it can have at {{{most}}} a {{{single}}} {{{y}}}-value for {{{each}}} {{{x}}}-value. Thus, a vertical line drawn at any x-position on the graph of a function will intersect the graph at {{{most}}}{{{ once}}}. 

here is the {{{vertical}}}{{{ line}}} {{{test}}}

{{{drawing( 600, 600, -10, 10, -10, 10,
blue(line(4,10,4,-10)),
 graph( 600, 600, -10, 10, -10, 10, 8,8)) }}}

as you can see, the  vertical blue line intersect the graph of {{{y=8}}} at {{{ one}}} point