Question

If the equation `y^2+x^2-10x+21=0` is satisfied by real values of `x` and `y`, prove that `x` lies between `3` and `7` and y lies between `-2` and `2`?

Answer 1

See below.

Explanation:

`y^2+x^2-10x+21=0 rArr (x-5)^2+y^2=2^2 rArr {(x in [5-2,5+2]),(y in [-2,2]):}`