Question 1012807
What's the coordinates to the fourth vertex of a rectangle
({{{-3}}},{{{2}}}), ({{{-3}}},{{{-1}}}), ({{{3}}},{{{-1}}}) 

The fourth vertex is ({{{3}}}, {{{2}}}). All four of the coordinates will share 1 {{{x}}} value and 1 {{{y}}} value with another one, which is what makes it a square/rectangle. This is the only combination that hasn't been done yet, and if you'll graph it you'll see that the point is in fact at ({{{3}}},{{{2}}}). 

{{{drawing(300,300,-5,5,-5,5,grid(1),
circle(-3,-1,.2),
circle(3,2,.2),
circle(3,-1,.2),circle(-3,2,.2),
locate(-3,-1,p(-3,-1)),
locate(3,-1,p(3,-1)),
locate(-3,2,p(-3,2)),
locate(3,2,p(3,2)),
green(  line(-3,-1,-3,2)),
green(  line(-3,2,3,2)),
green( line(-3,-1,3,-1)),
green( line(3,2,3,-1)))}}}