Value of ((x-y)^3+(y-z)^3+(z-x)^3) over k(x-y)(y-z)(z-x)

The same question, asked 3 times: CDS 2 2017*, CDS 1 2019*, CDS 2 2019. Every wording below, oldest first.

Try each one first, then open its answer.

Question 1
CDS 2 2017
34 $\frac{(x - y) (y - z) (z - x)}{(x - y)^3 + (y - z)^3 + (z - x)^3}$
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Question 2
CDS 1 2019
98 $\frac{(x-y)^3 + (y-z)^3 + (z-x)^3}{9(x-y)(y-z)(z-x)}$
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Question 3
CDS 2 2019
46 $\frac{(x - y)^3 + (y - z)^3 + (z - x)^3}{3(x - y)(y - z)(z - x)}$
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