Algebra: Plugging in Numbers

1. If $x$ is any negative integer less than $-6$, which of the following must be negative?

(A) $\dfrac{x^5}{-10}$

(B) $-2x$

(C) $x+(-x)$

(D) $\dfrac{x^2}{x+5}$

(E) $\dfrac{x}{-2}$

2. If $a+b=-20$, and $a>-7$, which of the following must be true?

(A) $b>-20$

(B) $b=-13$

(C) $b<-20$

(D) $b>-13$

(E) $b<-13$

3. $x(x-3)(x+7)$

For which of the following values is the value of the expression above negative?

(A) 3

(B) -7

(C) 0

(D) -9

(E) 10

4. If $mn=9$ and $m$ and $n$ are positive integers, what is a possible value of $4\centerdot m \centerdot m \centerdot \dfrac{m}{n}$?