hello,

If I have a point Q on O (geometric object) which is defined as the affine combination Q = aQ1 + bQ2 + cQ3, I think that the condition on the tuple (a, b, c) for the equation to be valid is a + b + c = 1, right? But I don't know why this must be true.

If that condition holds, what is the coordinate system defined by (a, b, c)?

Please it's urgent if anyone could help me appreciate it

thanks