Question

The graph of the equation $x^2+y^2=0$ in the three dimensional space is

• A. X-axis
• B. Y-axis
• C. Z-axis
• D. XY-plane.

Answer 1

Answer: (C)

$x^2+y^2=0\iff x=0$ and $y=0$
$\iff (x,y,z)=(0,0,z)\iff (x,y,z)$ lies on Z-axis