Question 93182
1)Given the binary operation * defined over the set of real numbers R by a*b=a+b+ab. What are the invertible elements of R with respect to *.

LET I BE THE IDENTITY ELEMENT WRT * OPERATION.SO
A*I=A=A+I+AI
I(A+1)=0
I=0
HENCE IF X IS INVERSE OF A THEN 
A*X=I=0=A+X+AX
X(A+1)= -A
X=-A/(A+1)
HENCE A SHOULD NOT BE -1
SO ALL ELEMENTS IN R EXCEPT A=-1 ARE INVERTIBLE