Monday

April 21, 2014

April 21, 2014

Posted by **Bonnie** on Tuesday, July 14, 2009 at 11:42pm.

(x+3)(x-5) < 0

I got so far on this and am lost..

(x+3 <0 and x-5>0) OR (x+3>0 and x-5<0)

(x<-3 and x > 5) OR (x> and x<5)

(x<-3 and x>5) OR (-3<x<5)

Do we use FOIL for this cause if we do i did this:

x^2-5x+3x-15

x^2-5x+3x-15

x^2-2x -15 >0

x^2 -4x-15>0

x<5, x<-3

x=-3 & x=5

Is any of this correct?

- Algebra -
**MathMate**, Wednesday, July 15, 2009 at 8:01am1. Do not use FOIL, because the problem is better solved as it is.

2. Visualize your numbers on the number line.

3. Only one of the two conditions on each side of (OR) is viable.

(x+3 <0 and x-5>0) OR (x+3>0 and x-5<0)

(x<-3 and x > 5) OR (x> and x<5)

(x<-3 and x>5) OR (-3<x<5)

It is impossible to have x<-3 AND x>5, so this case is eliminated. So (-3<x<5) is the right answer.

This question has been answered three times before, you can go through the different answers.

http://www.jiskha.com/display.cgi?id=1247616546

http://www.jiskha.com/display.cgi?id=1247545041

http://www.jiskha.com/display.cgi?id=1247541753

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