Question

In the xy-coordinate system above, line / (not shown) does not contain point in either quadrant II or

quadrant IV. Which of the following could be the equation of line /?
•x=3
•y=3x
•y=3x+3
•y=-3x-3

Answer 1

y=3x

Explanation:

If the line cannot be in quadrants II or IV, it must pass through the origin(0,0) and be in quadrants I and III.

Substitute (0,0) for y and x to find the answer.

1) x=3, 0=3 NO

2) y=3x, 0=3(0), 0=0 YES

3) y=3x+3, 0=3(0)+3, 0=3 NO

4) y=-3x-3, 0=-3(0)-3, 0=-3 NO

So the answer must be 2) y=3x