Sign-rules

Summary

\(a,b∈R\) :

• \(a+\left( -a \right)=0\)
• \(a+\left( -b \right)=a-b\)
• \(a-\left( -b \right)=a+b\)
• \(-\left( -a \right)=a\)
• \(-\left( a+b \right)=-a-b\)
• \(-\left( a-b \right)=-a+b\)
• \(a⋅\left( -b \right)=-\left( a⋅b \right)\)
• \(\left( -a \right)⋅b=-\left( a⋅b \right)\)
• \((-a)⋅\left( -b \right)=a⋅b\)