Question

$\ast$ is a binary operation on $Z$ such that:
$a\ast b=a+b+ab$.
The solution of $(3\ast 4)\ast x=-1$ is

• A. $1$
• B. $-1$
• C. $4$
• D. $3$

Answer 1

The correct option is B $-1$

$(3\ast 4)=(3+4)+(3\times 4)=7+12=19$...(i)
Now
$(3\ast 4)\ast x=19\ast x=19+x+19x=-1$ or $20x=-20$ or $x=-1$.
Hence the value of x is -1.