Question

is system (Z,*) is group for a*b=a+b-1
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Answer 1

Step-by-step explanation:

a∗b=a+b+1 (a,b,z is a group)

at a=−1⇒a∗b=−1+b+1=b

at b=−1⇒a∗b=a−1+1=a

⇒a∗0=a+0+1

⇒ identity element is −1.