Question 107025
{{{X^2+Y^2=25}}}
Solve for y as a function of x.
{{{Y^2=25-X^2}}}
{{{Y=sqrt(25-X^2)}}} and {{{Y=-sqrt(25-X^2)}}}
Since the square root cannot be negative, then
{{{25-X^2>=0}}}
{{{X^2<=25}}}
{{{abs(X)<=5}}}
The domain of x is {-5,5} and the range of y is {-5,5}. 
Choose several x's between -5 and 5 (-5,-4,-3,-2,-1,0,...) and calculate the y values. 
Examples, when x=-4,
{{{Y=sqrt(25-X^2)}}} and {{{Y=-sqrt(25-X^2)}}}
{{{Y=sqrt(25-(-4)^2)}}} and {{{Y=-sqrt(25-(-4)^2)}}}
{{{Y=sqrt(25-(16)^2)}}} and {{{Y=-sqrt(25-(16)^2)}}}
{{{Y=3}}} and {{{Y=-3}}}
So the ordered pairs (3,4) and (3,-4) are on your curve. 
More points make for a smoother curve. 
When you graph the function, you will see that it is the top and bottom of a circle centered at 0,0 with a radius of 5. 
{{{ graph( 300, 300, -6, 6, -6, 6, sqrt(25-x^2) , -sqrt(25-x^2)) }}}