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put this solution on YOUR website! When a root is at x=a then the factor is x-a.  So for x=-6 the factor is x+6, and for x=-1 the factor is x+1.  Multiplicity 3 means there are three factors (x+1).
Multiply the factors together to see the polynomial.
(x+6)(x+1)(x+1)(x+1) = 