Can someone explain to me how to factor 9x² - 6x - 24?

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Kim Kim
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Can someone explain to me how to factor 9x² - 6x - 24?

Thanks!
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Re: Can someone explain to me how to factor 9x² - 6x - 24?

9x² - 6x - 24
=  3(3x² - 2x - 8)   <— factored 3 out first
=  3(3x² - 6x + 4x - 8)   <— split -2x into two terms that multiply to get -24 and add to get -2...factoring by grouping
=  3[3x(x - 2) + 4(x - 2)]   <— factored 3x out of first two terms and 4 out of last two terms
=  3(3x + 4)(x - 2)   <— factored out the common factor, (x - 2)

- Proof