Question

Find the vector equations for medians from the vertices to the three midpoints of triangle ABC with vertices A(-1,5), B(5,-2) and C(3,5).

Answer 1

The equation is

2y + 85x + 75 = 0

Explanation:

Given vertices A(-1,5), B(5,-2) and C(3,5).

Suppose we want to find the median from A

First, we find the midpoint of side BC

Let the midpoint be M = ((x1 + x2)/2, (y1 + y2)/2)

= ((5+3)/2, (-2-5)/2)

= (8/2, -7/2)

= (4, -7/2)

Next, we write the equation of median with A(-1,5) and midpoint M(4,-7/2)

y = mx + c

The slope m = (y2 - y1)/(x2 - x1)

= (-7/2 - 5)/(4 + 1)

= (-17/2)/5

m = -85/2

We find the y-intercept, using A(-1,5)

x = -1, y = 5, m = -85/2

y = mx + c

5 = (-85/2)(-1) + c

c = 5- 85/2

= -75/2

y = -85x/2 - 75/2

Multiply through by 2

2y = -85x - 75

2y + 85x + 75 = 0

And this is the equation