z to the 5th power - 4z to the 4th power - 21 z to the third power

factor completely

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Factor completely:

`z^5-4z^4-21z^3`

Take out the first common factor of `z^3`

`therefore =z^3(z^2-4z-21) `

Now we can factorize the remaining bracket by using the factors of the 1st term (`z times z)` and those of the 3rd term that will render a middle term of -4 (that is, `7 times 3)`

`therefore = z^3(z+3)(z-7)`

**Ans: z^3(z+3)(z-7)**

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