# Expand powers of binomial expressions

1. Feb 12, 2016

### 3301

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. Feb 12, 2016

### SammyS

Staff Emeritus
You are attempting to distribute multiplication over multiplication.

a×(b×c) ≠ (a×b)×(a×c)

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
3. Feb 13, 2016

### HallsofIvy

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