SOLUTION: If (x &#8722; 7)(y + 7) < 0, then which of the following must be true? A. x > 7 B. y < &#8722;7 C. x < 7 D. y > &#8722;7 E. None of these.

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: If (x &#8722; 7)(y + 7) < 0, then which of the following must be true? A. x > 7 B. y < &#8722;7 C. x < 7 D. y > &#8722;7 E. None of these.       Log On


   

Question 286362: If (x − 7)(y + 7) < 0, then which of the following must be true?
A. x > 7 B. y < −7 C. x < 7 D. y > −7 E. None of these.
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
If %28x+-+7%29%28y+%2B+7%29+%3C+0, then either x-7%3C0 (ie x-7 is negative) or y%2B7%3C0 (ie y%2B7 is negative), but not both. If they are both negative, then the result is positive. Also, if they're both positive, then the product is positive.


So if x-7%3C0, then x%3C7 which is choice C)


and if y%2B7%3C0, then y%3C-7 which is is choice B)


So the answers are B and C (if you're allowed multiple answers), but not at the same time. If you aren't allowed multiple answers, then there's a typo somewhere.