Question 910385


{{{4x=y^2}}} does not define {{{y}}} as a function of {{{x}}}, because some value(s) of {{{x}}} have more than one {{{y}}}. 

In general,
{{{4x=y^2}}} =>{{{y=sqrt(4x)}}} or {{{y=-sqrt(4x)}}} 

=>{{{ y=2sqrt(x) }}} or {{{y=-2sqrt(x)}}} 

So, all the values of {{{x}}} larger than {{{ 0 }}} would have two {{{y}}} values.

For example, {{{x=16}}} would be paired with {{{y=2*4=8 and {{{y=-8}}}

A function cannot assign more than one {{{y }}}to any {{{x}}} value.