a − 0 = a {\displaystyle a-0=a} a × 0 = 0 {\displaystyle a\times 0=0} a / 0 = o o {\displaystyle a/0=oo}
a − ( − a ) = 2 a {\displaystyle a-(-a)=2a} a × ( − a ) = − a 2 {\displaystyle a\times (-a)=-a^{2}} a / ( − a ) = − 1 {\displaystyle a/(-a)=-1}
a − a = 0 {\displaystyle a-a=0} a × a = a 2 {\displaystyle a\times a=a^{2}} a a = 1 {\displaystyle {\frac {a}{a}}=1}
a n = a × a × a . . . × a {\displaystyle a^{n}=a\times a\times a...\times a} ( − a ) n = a n {\displaystyle (-a)^{n}=a^{n}} . n = 2 m {\displaystyle n=2m} ( − a ) n = − a n {\displaystyle (-a)^{n}=-a^{n}} . Với n = 2 m + 1 {\displaystyle n=2m+1}
1 = 1 {\displaystyle {\sqrt {1}}=1} ( − 1 ) = j {\displaystyle {\sqrt {(-1)}}=j}