The polynomial of degree 3\displaystyle {3}, P(x)\displaystyle {P}{\left({x}\right)}, has a root of multiplicity 2\displaystyle {2} at x=1\displaystyle {x}={1} and a root of multiplicity 1\displaystyle {1} at x=3\displaystyle {x}=-{3}. The y\displaystyle {y}-intercept is y=1.2\displaystyle {y}=-{1.2}.
Find a formula for P(x)\displaystyle {P}{\left({x}\right)}.
P(x)=\displaystyle {P}{\left({x}\right)}=   ,