To determine in which quadrant the triangle formed by the given coordinates is located, we need to analyze the coordinates of the vertices:
- \( (3, -1) \): This point is in Quadrant IV because the x-coordinate is positive and the y-coordinate is negative.
- \( (1, -3) \): This point is also in Quadrant IV for the same reason as above (positive x and negative y).
- \( (5, -3) \): This point is also in Quadrant IV (positive x and negative y).
All three points of the triangle are located in Quadrant IV. Therefore, the answer is:
4