3 points of a triangle, 21 bits to find

Okay, the title may not have made it very clear, but I have 3 vertexes of a triangle.

I need to find a bunch of stuff, all in Standard Form (Ax+By+C=0) with integer coefficients.

I'm pretty sure on my sides, but my friend says BC is wrong.

The Sides:

AB: 2x-y+5=0

BC: x+y-5=0

AC: 5x-y-7=0

If anyone can see if I got BC wrong, could you tell me? I don't need the answers themselves, I just need to see if I'm right.

As for the medians, I got the midpoints.

D is for AB

E is for BC

F is for CD

After that, I found the slopes. Then since I have A and B of the equation, I don't know which point to balance it out with (make it equal to 0).

So that's my first question. As these get answered I have more questions I'll tackle.

Thanks for taking the time to read this.

PS: First post!