Does the operation * defined below on the given set represent a binary operation? : `a**b=a+4b^2` on R

Does the operation * defined below on the given set represent a binary operation? : a**b=(a+b)/2 on N

Does the operation * defined below on the given set represent a binary operation? : a**b=ab on Z^+

Does the operation * defined below on the given set represent a binary operation? : a**b=a-b on Z^+

Let ** on the set integers I be a binary operation defined by a**b=3a+4b-2 . Find 4**5 .

Let * be a binary operation defined by a*b = 3a+4b-2 find 4*5

Let ** be a binary operatiion defined by a**b=3a+4b-2 .Find 4**5 ?

Is the binary operation ** defined on the set of integer Z by the rule a**b=a-b+2 commutative ?

Is the binary operation ** defined on the set of rational numbers by the rule a**b=ab//4 associative ?

Let A={1,2,3,4,5} . Write the operation table on the set A for the operation : ** where a**b=H.C.F.a and b for a,b in A