Question 900532
a is also a variable, but you would assume it has or could have a known value. a is a constant.


The distance from (0,0) to (4,y) must be a units.


Distance Formula for this, filled-in:
{{{sqrt((4-0)^2+(y-0)^2)=a}}}
{{{sqrt(16+y^2)=a}}}
{{{y^2+16=a^2}}}
{{{y^2=a^2-16}}}
{{{highlight(y=-sqrt(a^2-16))}}}  or  {{{highlight(y=sqrt(a^2-16))}}}