Question

What is the sign of −4ab when a>0 and b<0?

Answer 1

Answer:

A

Step-by-step explanation:

We have the expression:

$-4ab$

And we want to find its sign given that a>0 and b<0.

Notice that the expression is already negative since we have -4.

a>0 means that a is positive. Therefore, we can ignore it since it won’t do anything.

b<0 means that b is negative. Therefore, we will have two negatives being multiplied together. Hence, this will make a positive.

Therefore, the sign of our expression will be positive.

We can see this with an example. Let a=1 (1>0) and let b=-1 (-1<0). Then:

$-4(1)(-1)=4$

So, the sign is positive.

Hence, the answer is A.