Ask your own question, for FREE!
Mathematics 7 Online
OpenStudy (wintersuntime):

can someone help me with the problem Im about to post below please

OpenStudy (wintersuntime):

Find all the solutions to \[x^3+3x^2+2x \le0\]

OpenStudy (mathmale):

Ignore the "smaller than or equal to " symbol for now, and then find the roots of x^3 + 3x^2 + 2x = 0.

OpenStudy (mathmale):

Hint: Factor out x from all four terms.

OpenStudy (wintersuntime):

I don't get it

OpenStudy (mathmale):

If you don't get it, then ask some questions so that the problem will make more sense. If what I've suggested is not clear, point out what is not clear and guess what it means. You need to be involved in the solution of this problem.

OpenStudy (wintersuntime):

how do I factor out the x ?

OpenStudy (mathmale):

That's a lot better. Thank you. x^3 + 3x^2 + 2x = 0. --- --- --- --- x x x x Can you reduce each term? Note that 0/x is still 0.

OpenStudy (wintersuntime):

Yes

OpenStudy (mathmale):

Great. Reduce each term, one by one.

OpenStudy (wintersuntime):

ok

OpenStudy (wintersuntime):

Wouldn't it be 3+3^2+2=0

OpenStudy (mathmale):

In the first term, x^3 (read "x cubed" can be re-written as x*x*x, where * means "multiply." What is x^3 --- ? It's not 3. x

OpenStudy (wintersuntime):

x^2?

OpenStudy (wintersuntime):

or just 2

OpenStudy (mathmale):

Remember, I explained that x^3 means x*x*x. What is x*x*x ----- ? Hint: It's not 3, it's not 2. Here's the rule of exponents you need: x \[\frac{ x^m }{ x^m }=x ^{m-n}\]

OpenStudy (mathmale):

Hint: x^3 is \[x^m\]

OpenStudy (mathmale):

and x is\[x^n\]

OpenStudy (mathmale):

so, using m=3 and n=1, find\[\frac{ x^m }{ x^n }\]

OpenStudy (wintersuntime):

So it would be \[x^{3-1}\]

OpenStudy (wintersuntime):

which would give you x^2

OpenStudy (mathmale):

Yes, that's right.

OpenStudy (wintersuntime):

ok

OpenStudy (mathmale):

Please finish: x^3 + 3x^2 + 2x = 0. --- --- --- --- = x^2 + + = ? x x x x

OpenStudy (wintersuntime):

For 3x^2 what would happen with the 3

OpenStudy (mathmale):

Keep it. 3x^2 3x ---------- = --- = ? x^1 1

OpenStudy (wintersuntime):

2x

OpenStudy (mathmale):

Actually, that'd be 3x. It's the next term that would be 2 (not 2x).

OpenStudy (wintersuntime):

How did you get the 3x?

OpenStudy (mathmale):

So you've gotten this far in the factoring process: x(x^2 + 3x + 2 ) = 0 Hold the first x. Factor x^2 + 3x + 2.

OpenStudy (wintersuntime):

(x+2)(x+1)

OpenStudy (mathmale):

You should get two binomial factors: (x + ? ) (x + ? )

OpenStudy (wintersuntime):

so 2 and 1?

OpenStudy (mathmale):

(x+1)(x+2), yes. So, now you have x(x+1)(x+2)=0, in completely factored form.

OpenStudy (wintersuntime):

yes

OpenStudy (mathmale):

On the left side you have 3 factors. Set each one to 0 separately and solve each equation for x. The 3 values you find are your solution set.

OpenStudy (wintersuntime):

ok

OpenStudy (wintersuntime):

So it would be -2 for the first one

OpenStudy (wintersuntime):

-1 and 0

OpenStudy (mathmale):

Yes, very good. I'd write your solution set as {-2, -1, 0}.

Can't find your answer? Make a FREE account and ask your own questions, OR help others and earn volunteer hours!

Join our real-time social learning platform and learn together with your friends!
Can't find your answer? Make a FREE account and ask your own questions, OR help others and earn volunteer hours!

Join our real-time social learning platform and learn together with your friends!