Christos
Factor 15x^2 - 37x + 20
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hartnn
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do you know how to generally factor a quadratic ?
Christos
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I know some methods but I guess I miss this one
hartnn
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for \(ax^2+bx+c\), you need to find 2 numbers with sum = b and product = ac
so, for your question, you need to find 2 numbers with sum =-37 and product = 20*15 = 300
Christos
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I see now :)
hartnn
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so which 2 numbers u get ?
then split -37x accordingly...
Christos
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I got -20 and -15 what now?
hartnn
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good!
split -37x as -20x-15x
so, you have \(15x^2-15x-20x+20\)
there's a common factor in 1st 2 terms and a common factor in last 2 terms, can you proceed ?
hartnn
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oh wait, -20 and -15 are incorrect :P
Christos
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Yea :S
hartnn
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try another pair ?
Christos
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-12 -25 ?
hartnn
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bingo!
split -37x as -25x-12x
so, you have \(15x^2−25x−12x+20\)
there's a common factor in 1st 2 terms and a common factor in last 2 terms, can you proceed ?
Christos
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x(x15-25)4(3x + 5)
hartnn
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from first 2 terms factor out 5x
Christos
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5x(3x - 5) - 4(3x + 20)
hartnn
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-12x+20 = -4 (3x+.....?)
Christos
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its 5 sorry
hartnn
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+5 or -5 ?
Christos
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-5
hartnn
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so, now factor 3x-5 from that
Christos
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What do you mean? I dont understand :SS
hartnn
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5x (3x-5) -4(3x-5)
factor out 3x-5
(3x-5)(5x-4)
i meant this, and you're done
LadyKatsaTheGraceling
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Bonjour! Comment allez vous?
hartnn
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i am fine, do u need any help ? with what ?
LadyKatsaTheGraceling
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You are very good at teaching people
hartnn
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oh, thank you very much :) :D
some_someone
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\[15x^2 - 37x + 20 \]
\[(3 x-5) (5 x-4)\]