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Homework Help: Expand powers of binomial expressions

  1. Feb 12, 2016 #1
    1. The problem statement, all variables and given/known data

    The problem comes in second term after 4(2z....)
    2. Relevant equations

    3. The attempt at a solution
    so i got 4 (8z^3) 5k.
    32 (z^3) * (20k). After that i left it like that but I supposed to get answer like this
    160 z^3 * k

    I can conjoin constants of z and k variables? Or am I missing something else
    Last edited: Feb 12, 2016
  2. jcsd
  3. Feb 12, 2016 #2


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    You are attempting to distribute multiplication over multiplication.

    a×(b×c) ≠ (a×b)×(a×c)

    Added in Edit:
    To put it another way:

    32 (z^3) * (20k) is just an extended multiplication. There is no adding going on.

    32 (z^3) * (20k) is simply (32)⋅(z3)⋅(20)⋅(k)
    Last edited: Feb 13, 2016
  4. Feb 13, 2016 #3


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    4*8= 32 but where did the "20" come from? 4(8)(5)= 32(5)= 160.

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