Help with inequalities

• May 25th 2008, 05:07 PM
lizann
Help with inequalities
Yes, it's me again and I need more help. This time I couldn't do anything with this problem because I really did not understand this one. Here is the problem: (x+6)(x-16)(x+5)>0; The solution set is (xl ).
• May 25th 2008, 05:19 PM
mr fantastic
Quote:

Originally Posted by lizann
Yes, it's me again and I need more help. This time I couldn't do anything with this problem because I really did not understand this one. Here is the problem: (x+6)(x-16)(x+5)>0; The solution set is (xl ).

Draw a graph of y = (x+6)(x-16)(x+5). For what values of x is it above the x-axis (that is, y > 0)?
• May 25th 2008, 05:34 PM
Krizalid
Make the following table:

http://img181.imageshack.us/img181/4...9460e7djr6.gif

• In the first column, identify the factors and the expression that you want to analize.
• Following up on this, find where the expressions get zero and identify every interval as it's written above.
• Pick a number of the interval and substitute it into the factors to see the sign in such interval.
• Finally multiply vertically to see the sign of the whole expression.

We require the positive sign, so the solution set is $S=(-6,-5)\cup (16,\infty ).$
• May 25th 2008, 06:30 PM
lizann
Thank you
Thanks for the help very much appreciated.(Hi)