1983 AMC 12 Question 13
AMC12 · 1983 AMC 12
If $xy=a,$ $xz=b,$ and $yz=c,$ and none of these quantities is $0,$ then $x^2+y^2+z^2$ equals
$\frac{ab+ac+bc}{abc}$
$\frac{a^2+b^2+c^2}{abc}$
$\frac{(a+b+c)^2}{abc}$
$\frac{(ab+ac+bc)^2}{abc}$
$\frac{(ab)^2+(ac)^2+(bc)^2}{abc}$