Hello,

I'll try. I did it on a paper and just noticed a tiny mistake, so I'll go freely while typing lol ! But you gotta check it because I'm sure I won't get the result you're given

If P(x) has multiple roots (one or more or all roots are multiple ?), then there exists m such that

(1) and (2)

From (2), we get or

If m=0, then b=0 by (1).

Let's say otherwise that's not funny

So

Substituting in (1) :

Take the 3rd power of both sides :

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Remember that

We have (I write it in the same order so that you can see) :

and

and similarly

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Which is too similar to be a big mistake