Answer:
3 units
Explanation:
Because points M and N have the same y-coordinate, to find the length of MN, all we have to do is find the difference of the x-coordinates of the two points. Therefore, the answer is |-4 - (-1)| = |-4 + 1| = -3 = 3 units. The reason for the absolute value is to ensure that our answer will always be positive no matter what order we subtract in. This matters because the length of a line segment cannot be negative.