the numbers a and b are negative in nature.the sign of which of te following expressions cannot be determined with certainty?

a.a+b

b.a-b

c.a*b

d.a divided by b

We know our numbers a And b are in negative in sign , For checking uncertainty we replace a = -a And b = - b in all options And observe uncertainty . As:

a ) a + b = - a + (- b ) = - ( a + b)

So we can say that with certenity that ( a + b ) never be equal to - ( a + b)

b ) a - b = - a - ( - b) = - a + b , here we can't determine with certainty that final answer is positive or negative.

c ) a b = - a ( -b) = ab

d) $\frac{a}{b}=\frac{-a}{-b}\Rightarrow \frac{a}{b}$

**So only in option B we can't be determined with certainty . ( Ans)**

**
**