|a|=2.2,
a=2.2
a=-2.2
|b|=1.8,
b=1.8
b=-1.8
|a+b|=|2.2+1.8|=4
|a+b|=|-2.2+1.8|=0.4
|a+b|=|2.2-1.8|=0.4
|a+b|=|-2.2-1.8|=4