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Mathematics 21 Online
OpenStudy (anonymous):

Solving equation help please???

OpenStudy (anonymous):

I tested every answer here and none of them were equal to zero, what am I doing wrong?

TheSmartOne (thesmartone):

We could factor by grouping..

TheSmartOne (thesmartone):

\(\ 9x^3 +9x^2-4x-4\) Do you know how to factor by grouping? @JoeJoldin

OpenStudy (anonymous):

Sort of, will the next step look like this?: x^3 + x^2 - 4 - 1

TheSmartOne (thesmartone):

Umm. no

TheSmartOne (thesmartone):

\(\ 9x^3 +9x^2-4x-4\) We would seperate the first 2 terms and facotr them and sperate the last two terms and factor them..

TheSmartOne (thesmartone):

\(\ 9x^3 +9x^2~~~~~~~~~~~~~-4x-4\) \(\ 9x^2(x+1) ~~~~-4x-4\) and then we factor the other half.

OpenStudy (anonymous):

not sure how to do that

TheSmartOne (thesmartone):

-4x-4 What is common?

OpenStudy (anonymous):

4

TheSmartOne (thesmartone):

More like -4

TheSmartOne (thesmartone):

And then we will get \(\ 9x^2(x+1) ~-4(x+1)\)

TheSmartOne (thesmartone):

And if we take out (x+1) from it we can get it factored!

OpenStudy (anonymous):

So now its just 9x^2-4?

TheSmartOne (thesmartone):

Umm more like \(\ (x+1)(9x^2-4)\)

TheSmartOne (thesmartone):

And we just set each one equal to 0

OpenStudy (anonymous):

So what do I do now

TheSmartOne (thesmartone):

\(\ x+1=0\) and \(\ x^2-4=0\)

OpenStudy (anonymous):

My answer must be B then right?

TheSmartOne (thesmartone):

Well there is no correct answer...

TheSmartOne (thesmartone):

All of those answer choices are wrong..

OpenStudy (anonymous):

yeah this has got me lost

TheSmartOne (thesmartone):

And I am pretty sure I did everything correct.

TheSmartOne (thesmartone):

@ParthKohli @Jhannybean Can check for me :P

TheSmartOne (thesmartone):

Plugging in choices now.. And A isn't correct...

Parth (parthkohli):

\[9x^2 - 4 = 0\]\[x+1 = 0\]

TheSmartOne (thesmartone):

Yeah got that too.

OpenStudy (ankit042):

I am getting B as the answer

Parth (parthkohli):

\[(3x + 2)(3x - 2) = 0\]\[x+ 1 = 0\]

TheSmartOne (thesmartone):

Oh wait B is the answer.

TheSmartOne (thesmartone):

I should go to sleep now..

TheSmartOne (thesmartone):

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