Mathematics
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OpenStudy (anonymous):
Solving equation help please???
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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
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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
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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
\(\ (x+1)(9x^2-4)\)
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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...
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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...
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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.
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TheSmartOne (thesmartone):
I should go to sleep now..
TheSmartOne (thesmartone):
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