SOLUTION: How do you find the other endpoint of a line when given the midpoint and one endpoint?

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Question 897228: How do you find the other endpoint of a line when given the midpoint and one endpoint?
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
To find the midpoint of two endpoints
xm, ym are the x,y of the midpoint
x1, y1 are the x,y of one endpoint
x2, y2 are the x,y of the other endpoint
xm=(x2+x1)/2
ym=(y2+y1)/2
To find the endpoint knowing one endpoint and the midpoint
solve for x1 and y1
x1=2*xm-x2
y1=2*ym-y2