Question

In three dimensional space, the equation $x^2-x-2=0$ represents

• A. a pair of straight lines
• B. a set containing two distinct points
• C. a pair of parallel planes
• D. none of these

Answer 1

Answer: (C)

$x^2-x-2=0\iff (x-2)(x+1)=0$
$\iff x=2,x=-1$ which are the planes (both parallel to YOZ plane).