Question

If x and y are negative integers, which of the following expressions must be negative?
A. xy
B. x + y
C. x- y
D. x^2 + y^2
E. x^2 - y^2

Answer 1

What do you think?

Answer 2

Well, I know that it's not a.

Answer 3

It's either B or E.

Answer 4

Wait, is the answer B?

Answer 5

Only one way to find out. Replace a and b with -a and -b respectively and see the result.

Answer 6

Negative. Same thing with E.

Answer 7

What happens if you square(or raise to an even power) a negative number?

Answer 8

Wouldn't it be positive?

Answer 9

Yes. So what would E give you?

Answer 10

Positive/negative. Since the question said "MUST", then that can't be the answer.

Answer 11

I guess the best choices in B.

Answer 12

Correct. B is not the best choice, it IS the answer :)

Answer 13

Hehe. I like that.