The positions of real numbers a and B on the number axis are shown in the figure. Try to simplify | a + B | + | A-B | + | ab| -----b--------0--------a--------》

The positions of real numbers a and B on the number axis are shown in the figure. Try to simplify | a + B | + | A-B | + | ab| -----b--------0--------a--------》

Let | B | be | a | and | B | be | B | a | then a + B | 0, A-B | 0, ab | 0, so | a + B | + | A-B | + | ab | = - A-B + a-b-ab = - 2b-ab