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anonymous

  • 5 years ago

simplify (3a-4b^3)^3 Can anyone help me? Should it be 27a^3-64b^9? Mathway has some crazy answer...

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  1. anonymous
    • 5 years ago
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    no it is 27a^3 - 72a^2b^3 - 96ab^6 + 64b^9

  2. anonymous
    • 5 years ago
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    how did you get the middle part? i don't get it.

  3. anonymous
    • 5 years ago
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    did you use foil and do the equation times itself then foil again for the 3rd time?

  4. anonymous
    • 5 years ago
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    cubic expansion is a^3 + a^2b + b^2a + b^3 for ( a + b ) ^ 3 its different from squaring

  5. anonymous
    • 5 years ago
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    ok- thanks.

  6. anonymous
    • 5 years ago
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    what you have as the "should be " answer

  7. anonymous
    • 5 years ago
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    is the expansion of ( 3a)^3 - (4b^3)^3

  8. anonymous
    • 5 years ago
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    is that correct though? if i was just asked to simplify?

  9. anonymous
    • 5 years ago
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    = (3a - 4b^3)( 9a^2 +12ab^3 + 16b^6)

  10. anonymous
    • 5 years ago
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    ahh ignore what I wrote above lol , I thought you meant that was the answer the textbook had

  11. anonymous
    • 5 years ago
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    no, that was my answer. i see- so it is wrong.

  12. anonymous
    • 5 years ago
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    well, I am guessing they said expand and simplify, because something factor is alot more simple than a messy cubic expansion

  13. anonymous
    • 5 years ago
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    it is just a post i have to answer...simplify and then the equation.

  14. anonymous
    • 5 years ago
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    i will write what i thought- seems a lot simpler than your way :)

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spraguer (Moderator)
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