The plus sign is in front of the bracket, and the constant sign is in the bracket;

There is a negative sign in front of the brackets, and the items in the brackets should change sign, positive to negative, negative to positive;

Now, for example:

(X 1-X2)+(Y 1-Y2)

Because there is a plus sign in front of both brackets, the numbers in both brackets are the same symbol;

(X 1-X2)+(Y 1-Y2)

=X 1-X2+Y 1-Y2

Example 2, (X 1-X2)-(Y 1-Y2)

Since the last bracket is preceded by a minus sign, the items in brackets should be changed.

(X 1-X2)-(Y 1-Y2)

=(X 1-X2)-Y 1+Y2

Where Y 1 becomes -Y 1 and -Y2 becomes y2;