i don't get how to do this cause i dunt think you can factor it

how do u solve this inequality

x^3+3x^2-18x < and equal to 22

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- Jun 23rd 2007, 09:21 AMcalchelpUrgent How Do U Find The Inequality For This
i don't get how to do this cause i dunt think you can factor it

how do u solve this inequality

x^3+3x^2-18x < and equal to 22

??????????????????????????????? - Jun 23rd 2007, 10:13 AMCaptainBlack
- Jun 23rd 2007, 10:41 AMearboth
Hello,

you asked this question already. I couldn't get a simple solution and I can only show you how to get some approximations:

1. you only can factor the LHS of this inequality:

but I don't know how to use this "result".

2. What I did:

Consider the function:

Calculate the zeros of f by the Newton method. I got:

Using these values to 2 sign. digits you can factor the term f(x) into:

Now calculate

A product of 3 factors is negative (that's the same as lower zero) if 2 factors have the same sign and one factor is negative. Thus you'll get a system of linear inequalities:

Now solve these inequalities for x. The final result should be:

I've attached diagrams of the graph of and . Those parts of the graph which are**below**y = 22 are marked in green or red.