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[SOLVED] Solve the inequality...and justify your answer

Raerin

Member
Oct 7, 2013
46
Solve the inequality 12x^3 + 8x^2 ≤ 3x + 2 and justify your answer.

To justify the answer do you need to make a sin chart and graph it?
 

Petrus

Well-known member
Feb 21, 2013
739
How do you solve third degree polynom? Do you know what rational root Theorem is?
 

Klaas van Aarsen

MHB Seeker
Staff member
Mar 5, 2012
8,780
Solve the inequality 12x^3 + 8x^2 ≤ 3x + 2 and justify your answer.

To justify the answer do you need to make a sin chart and graph it?
Hi Raerin! :)

The usual approach is to first solve the equality.
Then take the derivative and find its roots.
Then you can make a sign chart to read off the solution (did you mean a sign chart instead of a sin chart?)

The first step is already not so easy for this particular problem.
As Petrus suggested, the easiest way to find the roots is by using the Rational root theorem.
Do you know of it?
 

Raerin

Member
Oct 7, 2013
46
Hi Raerin! :)

The usual approach is to first solve the equality.
Then take the derivative and find its roots.
Then you can make a sign chart to read off the solution (did you mean a sign chart instead of a sin chart?)

The first step is already not so easy for this particular problem.
As Petrus suggested, the easiest way to find the roots is by using the Rational root theorem.
Do you know of it?

Oops, I made a typo, so yes, I do mean sign chart.
You're supposed to bring everything to one side, right? Then you find the number that would make the polynomial = 0?
 

Klaas van Aarsen

MHB Seeker
Staff member
Mar 5, 2012
8,780
Oops, I made a typo, so yes, I do mean sign chart.
You're supposed to bring everything to one side, right? Then you find the number that would make the polynomial = 0?
Yep!