Raeee_009
x^2-9x+20 factorise quadratics
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nubeer
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familiar with quadratic formula?
Raeee_009
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no :(
cwrw238
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this one can be factorized
hartnn
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can u factorize @Raeee_009 ?
hba
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Quadratic formula
\[x=-b \pm \sqrt{b^2-4ac}/2a\]
nubeer
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\[x = \frac{ -b \pm \sqrt{b ^{2}-4ac } }{ 2a}\]
this is the quadratic formula
now look at your equation it's x^2-9x+20
so a =1 ,b = -9 , c = 20
just plug in values you will get 2 values of x
Raeee_009
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that is so confusing
cwrw238
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yes - you asked about factoring
quadratics factor to the form
(x +/- a)(x +/- b)
cwrw238
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to find a and b you need the product ad = +20 and sum = -9
can u think of 2 numbers which fit this requirement?
cwrw238
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* product ab = + 20
Raeee_009
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hmm.. still don't get it :(
cwrw238
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20 = -4 * -5 right?
Raeee_009
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yeah
cwrw238
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and -4 + -5 = ?
hba
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|dw:1353601861741:dw|
Raeee_009
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-9
cwrw238
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so thats your values of a and b
hba has illustrated the process in his drawing
Raeee_009
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ohh im understanding a bit now so is the answer (x-4) (x+9)
cwrw238
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yea
hba
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@cwrw238 No.
cwrw238
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hba - your method is slightly different to mine - true
hba
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I am talking about the answer she got ?
cadex
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(x-4)(x-5)
cwrw238
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oh yes - i misread it (x - 4)(x - 5) is correct solution
a = -4 and b = -5 raee_009
hba
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@Raeee_009 Please see my illustration and try to learn ? Where are you getting confused ?
Raeee_009
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ohhhh! i get it now! thank you so much eveyone
hba
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Your'e welcome.
Raeee_009
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one quick question does a + and - = - ?
hba
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Well (+)(+)=+
(+)(-)=-
(-)(-)=+
Got it ?
Raeee_009
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ohh yeah thanks :D
Raeee_009
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so would x^2-6x-7=(x-7)(x+1)
cwrw238
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right
hba
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|dw:1353603740199:dw| @Raeee_009 Awesome :D