## System of equations: x^n + y^n + z^n, n=1,2,3,4

What is    $x + y + z$,    if the following are given

$x^2 \; + \; y^2 \; + \; z^2$
$x^3 \; + \; y^3 \; + \; z^3$
$x^4 \; + \; y^4 \; + \; z^4$