Math Problem Statement

CD has a midpoint at M(–5, –5). Point C is at (–1, –6). Find the coordinates of point D.

Solution

To find the coordinates of point DD, we can use the midpoint formula. The formula for the midpoint M(xm,ym)M(x_m, y_m) of a line segment with endpoints C(x1,y1)C(x_1, y_1) and D(x2,y2)D(x_2, y_2) is:

M=(x1+x22,y1+y22)M = \left( \frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2} \right)

Given:

  • Midpoint M=(5,5)M = (-5, -5)
  • Point C=(1,6)C = (-1, -6)

Let D(x2,y2)D(x_2, y_2) represent the unknown point.

Using the midpoint formula:

5=1+x22(for the x-coordinates)-5 = \frac{-1 + x_2}{2} \quad \text{(for the x-coordinates)} 5=6+y22(for the y-coordinates)-5 = \frac{-6 + y_2}{2} \quad \text{(for the y-coordinates)}

Now, solve these equations:

  1. For the x-coordinate: 5=1+x22-5 = \frac{-1 + x_2}{2} Multiply both sides by 2: 10=1+x2-10 = -1 + x_2 Add 1 to both sides: x2=9x_2 = -9

  2. For the y-coordinate: 5=6+y22-5 = \frac{-6 + y_2}{2} Multiply both sides by 2: 10=6+y2-10 = -6 + y_2 Add 6 to both sides: y2=4y_2 = -4

Thus, the coordinates of point DD are (9,4)(-9, -4).

Would you like more details or have any questions about the solution?

Here are 5 related questions to expand this topic:

  1. How would you find the distance between points CC and DD?
  2. What is the slope of the line passing through points CC and DD?
  3. Can you calculate the equation of the line passing through CC and DD?
  4. How would you solve for the coordinates of point DD if CC were different?
  5. What happens to the midpoint if the coordinates of CC and DD are changed?

Tip: The midpoint formula is useful when working with geometry problems involving bisectors or symmetry!

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Math Problem Analysis

Mathematical Concepts

Coordinate Geometry
Midpoint Formula

Formulas

Midpoint formula: M = ((x1 + x2)/2, (y1 + y2)/2)

Theorems

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Suitable Grade Level

Grades 8-10