### 12.6.3 The difference and sum of two points in the plane:+, -

Let A and B be two points in the plane, with affixes a1 + i a2 and b1 + ib2 respectively.
Input:

A:= point(1 + 2*i); B := point(3+4*i)

- The difference B-A returns the affix (b1−a1)+i(b2−a2), which represents the vector AB.
  Input:
  vector(A,B); vector(point(0),point(B-A))
  Output:
- The sum B+A returns the affix (b1+a1)+i(b2+a2). If D := point(B+A), then BD = OA.
  Input:
  D := point(B + A);
  segment(B,D); segment(point(0),A)
  Output:

Note that -A is the point symmetric to A with respect to the origin.

The sum of three points A + B + C can be viewed as the translate of C by the vector A + B. So if A or B contains parameters, you should write this as C + (A + B) or evalc(A + B) + C.