Answer: xy = 0.
- A x + y = 0
- B x - y = 0
- C xy = 0
- D x² + y² = 0
Correct answer: C. xy = 0
Explanation: x-axis: y = 0; y-axis: x = 0. Combined: xy = 0.
The slope of a line is the ratio of vertical change (rise) to horizontal change (run) between any two points on it - equivalently, the tangent of the angle θ the line makes with the positive x-axis.