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x^2-2x-24=0

 Apr 26, 2014

Best Answer 

 #3
avatar+109520 
+5

Hi Bioschip,

I really like your logic there.  And of course you are correct.  6 IS ONE of the answers !   

When you have an equation like this with an x2 term, there are usually 2 answers.

this is how it is done.   

$$x^2-2x-24=0$$ 

First I need to factorise this.  Factors are things that multiply to get the answers

I need 2 numbers that multiply to -24  (one will need to be neg and one pos)

they also need to add to -2   (How about -6 and 4, they work)

so the question becomes

$$(x-6)(x+4)=0$$      that is what Bertie got up to!

NOW, if two things multiply together to give 0 then one of them (or both of them) must equal 0.

so either $$x-6=0$$  or  $$x+4=0$$

so   $$x=6$$   OR    $$x=-4$$  

Maybe you would like to try this one   $$x^2+5x+4=0$$   ???

----------------------------------------------------------

NOW I want people to start learning to use LaTex which is how we display the maths stuff.

So here is a little lesson.

Press the LaTex button, type (x-6)(x+4)=0  then press ok.

See how it displays.  

If you want to know how to display anything else, please ask.  Remember, Members get priority answering.  

-----------------------------------------------------------------

 Apr 26, 2014
 #1
avatar+158 
+5

if you are looking for the value of x then that is six because if you use Pedmas then 6^2 comes first and that is equal to 36 then your problem is equal to 36-2x-24=0 then you use 2*6 get 12 and your problem is equal to 36-12-24=0 so you probably no what to do on from there 36-12=24 and 24-24=0.

 Apr 26, 2014
 #2
avatar+890 
+5

(x - 6)(x + 4) = 0.

 Apr 26, 2014
 #3
avatar+109520 
+5
Best Answer

Hi Bioschip,

I really like your logic there.  And of course you are correct.  6 IS ONE of the answers !   

When you have an equation like this with an x2 term, there are usually 2 answers.

this is how it is done.   

$$x^2-2x-24=0$$ 

First I need to factorise this.  Factors are things that multiply to get the answers

I need 2 numbers that multiply to -24  (one will need to be neg and one pos)

they also need to add to -2   (How about -6 and 4, they work)

so the question becomes

$$(x-6)(x+4)=0$$      that is what Bertie got up to!

NOW, if two things multiply together to give 0 then one of them (or both of them) must equal 0.

so either $$x-6=0$$  or  $$x+4=0$$

so   $$x=6$$   OR    $$x=-4$$  

Maybe you would like to try this one   $$x^2+5x+4=0$$   ???

----------------------------------------------------------

NOW I want people to start learning to use LaTex which is how we display the maths stuff.

So here is a little lesson.

Press the LaTex button, type (x-6)(x+4)=0  then press ok.

See how it displays.  

If you want to know how to display anything else, please ask.  Remember, Members get priority answering.  

-----------------------------------------------------------------

Melody Apr 26, 2014

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