The binary operation on the set of real numbers is defined by $m*n = \frac{mn}{2}$ for all $m, n \in R$. If the identity element is 2, find the inverse ...

Assessment: JAMB UTME - Mathematics - 2012 Subject: General Mathematics

Question 1 Report

The binary operation on the set of real numbers is defined by $m*n = \frac{mn}{2}$ for all $m, n \in R$. If the identity element is 2, find the inverse of -5

- \frac{4}{5}

-

- \frac{2}{5}

4

5

Answer Details

m $\propto$ n = $\frac{m n}{2} - a$
Identify = e = 2
a $\propto$ a-1 = e
a $\propto$ a-1 = 2
-5 $\propto$ a-1 = 2
$\frac{- 5 \times a^{- 1}}{2} = 2$
$a^{- 1} = \frac{2 \times 2}{- 5}$
$a^{- 1} = - \frac{4}{5}$