Answers

2015-09-09T21:34:15+05:30
On Z,* is define by a*b=a-b
it can be observed that 1*2=1-2=1 and 2*1=2-1=1
∴1*2≠2*1; where 1 and 2∈Z
Hence, the operation* is not commutative
we have
(1*2)*3=(1-2)*3= -1*3= -1-3= -4
1*(2*3)=1*(2-3)=1*-1=1-(-1)=2
∴(1*2)*3≠1*(2*3);where 1,2 and 3 are ∈Z
hence, the operation* is not commutative
0