Question

[hieu le]

rut gon bieu thuc

|a| - a 

Answer 1

[Long O Nghẹn]

I a I - a

= a - a

=0

Answer 2

[Tran Manh Hung]

TH1:|a|=a

=> |a|-a=a-a=0

TH2:|a|=-a

=> |a|-a=(-a)-a=-2a