Find the slope of your given points (rise over run) or (y2-y1 over x2-x1)
6-10=-4
2-4=-2
Because both sums were negative, the slope becomes positive. Also, 4/2 reduces to 2/1 or just 2.
Now, if the slope was 2 from one endpoint to the MIDpoint, the the slope will be the same to the other endpoint.
