ineedyouubiebs
Factor the polynomial: 54k^2-24
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ineedyouubiebs
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@jim_thompson5910 Help?
jim_thompson5910
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hint:
54k^2 - 24
6(9k^2 - 4)
ineedyouubiebs
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Where did you get the 9k^2 in the second line?
jim_thompson5910
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I factored out 6 from the expression
jim_thompson5910
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54k^2 - 24
6*9k^2 - 6*4
6(9k^2 - 4) .. using the distributive property
ineedyouubiebs
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@jim_thompson5910 oh okay I get it, but then there's no number that multipies to give -4 and adds to 9? thats where im stuck at
jim_thompson5910
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from here, you would use the difference of squares rule to factor
jim_thompson5910
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and 9k^2 - 4 is really 9k^2 + 0k - 4
so you need to find two numbers that multiply to 9*(-4) = -36 and add to 0, then you factor by grouping
or you can use the difference of squares rule to factor
ineedyouubiebs
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the difference of squares rule?
jim_thompson5910
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difference of squares
a^2 - b^2 = (a - b)(a+b)
jim_thompson5910
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ex:
25x^2 - 49
(5x)^2 - (7)^2
(5x - 7)(5x + 7)
So 25x^2 - 49 factors to (5x - 7)(5x + 7)
timo86m
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|dw:1376179696291:dw|
ineedyouubiebs
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im sorry im still confuse by this
timo86m
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basically it has to do with common factors
jim_thompson5910
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did you see my factoring example with 25x^2 - 49
jim_thompson5910
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so use that to factor 9k^2 - 4
ineedyouubiebs
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Following your example so far I've got (3K)^2-(2)^2
ineedyouubiebs
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@jim_thompson5910
jim_thompson5910
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keep going
ineedyouubiebs
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I got (3x-2)(3x-2) ?? @jim_thompson5910
jim_thompson5910
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close, very close
jim_thompson5910
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but not quite
ineedyouubiebs
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where did i go wrong?
jim_thompson5910
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the difference of squares rule is
a^2 - b^2 = (a - b)(a+b)
jim_thompson5910
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notice how it's minus, then plus (not two minuses)
jim_thompson5910
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it's NOT
a^2 - b^2 = (a - b)(a-b)
ineedyouubiebs
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so then its (3x-2)(3x+2)
jim_thompson5910
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the final answer is 6(3k-2)(3k+2)