# Distance between two points and the midpoint

The distance formula is an algebraic expression used to determine the distance between two points with the coordinates (x_{1}, y_{1}) and (x_{2}, y_{2}).

$$D=\sqrt{(x_{2}-x_{1})^{2}+(y_{2}-y_{1})^{2}}$$

**Example**

Find the distance between (-1, 1) and (3, 4).

This problem is solved simply by plugging our x- and y-values into the distance formula:

$$D=\sqrt{(3-(-1))^{2}+(4-1)^{2}}=$$

$$=\sqrt{16+9}=\sqrt{25}=5$$

Sometimes you need to find the point that is exactly between two other points. This middle point is called the "midpoint". By definition, a midpoint of a line segment is the point on that line segment that divides the segment in two congruent segments.

If the end points of a line segment is (x_{1}, y_{1}) and (x_{2}, y_{2}) then the midpoint of the line segment has the coordinates:

$$(\frac{x_{1}+x_{2}}{2},\: \frac{y_{1}+y_{2}}{2})$$

**Video lesson**

Find the midpoints between the coordinates (-4, -1) and (6,7)