$3\mathrm{.}4.$ Find the minimum value $of{x}^2+y^2+z^2$ subject $to$ the constraints $x+y-z=0$

and $x+3y+z=2.$ Give a geometrical interpretation $of$ your answer and

using your interpretation explain why $x^2+y^2+z^2$ has $no$ maximum subject

$to$ these constraints.