Question

Point C is at (-9, -2) and point M is at (-1, 4). Point M

is the midpoint of the line segment whose endpoints
are C and D.
What are the coordinates of endpoint D?

Answer 1

The answer is (7, 10).

Remember the midpoint formula :
`\boxed {M = ((x_(1)+x_(2))/(2),(y_(1)+y_(2))/(2))}`

Finding the x coordinate of D

• x = (x₁ + x₂) ÷ 2
• -1 = (-9 + x₂) ÷ 2
• -2 = -9 + x₂
• x₂ = 7

Finding the y coordinate at D

• y = (y₁ + y₂) ÷ 2
• 4 = (-2 + y₂) ÷ 2
• 8 = -2 + y₂
• y₂ = 10

Answer 2

The coordinates of D is (7, 10)

Step-by-step explanation:

Let the coordinates of endpoint D be (x, y)

Mid-point formula:

`\sf (x_m, y_m) = ((x_1+x_2)/(2), (y_1+y_2)/(2))`

Applying formula:

`\sf (-1, \:4) = ((-9+ x)/(2),\: (-2+y)/(2) )`

Comparing found:

`\sf -1 =(-9+ x)/(2) \quad and \quad \: 4 = (-2+y)/(2)`

`\sf 2(-1)+9 =x \quad and \quad \: 2(4)+2 =y`

`\sf x = 7 \quad and \quad \: y = 10`

So, coordinates of D is (7, 10)