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jmc

algebra senior

Problem

Suppose and . Which of the following must be true?



Enter your answer as a list of those options that are always true. For instance, if you think only the first and third are true, enter A, C.
Solution
Consider a negative and a positive . Then is positive and is negative, and hence this is not true. If we consider negative numbers for all three variables, , and hence this is not true. Consider a negative and a positive . Then is positive and is negative, hence this is not true. Subtracting from both sides gives us which we know is true. If is positive then is negative and . If is negative, then which means .

Thus, are always true.
Final answer
D, E