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mzapata29

  • 3 years ago

Not understanding how to work sum of cubes 125x^3+27y^3

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  1. matricked
    • 3 years ago
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    do u need to factor them

  2. matricked
    • 3 years ago
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    then use a^3+b^3= (a+b)(a^2 -ab+b^2)

  3. matricked
    • 3 years ago
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    for a^3-b^3= (a-b)(a^2 +ab+b^2)

  4. agent0smith
    • 3 years ago
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    \[ 125x^3+27y^3 = (5x)^3 + (3y)^3\]

  5. matricked
    • 3 years ago
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    if u need not factor them then use a^3+b^3 =(a+b)^3 -3ab(a+b)

  6. agent0smith
    • 3 years ago
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    Now a = 5x and b =3y.

  7. matricked
    • 3 years ago
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    125x^3+27y^3 =(5x)^3 +(3y)^3 =(5x+3y)(25x^2 -15xy +9y^2)

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