although this question i'm having trouble with is in calculus,
it's really in the chapter about vectors before multivariable calculus.

the question goes like this:

i need to give an example of a circle centered at the point Q,
in which the points - A(7, -7) and B(-4, 6) are on that circle
and the angle AQB equals to pi/2.

basically this looks like a pretty easy question,
i've called the coordinates of Q - (q1, q2),
and created the two vectors AQ [q1-7, q2+7] and QB [-4-q1, 6-q2].
obviously the dot product of the two should be equal to 0 in order for the
angle between the two vectors to be pi/2, and also the length
of AQ and QB should be the same in order for both A and B being on the

please help - cause i've tried running over the algebra of this and got
to some pretty nasty figures again and again, and worst yet that these
figures are also not correct...

thanks in advance and sorry for the long preface