easy
the factorrs of an equation that has the roots, r1,r2,r3,r4 is (x-r1)(x-r2)(x-r3)(x-r4)
also, remember that if it has real coefieints, and a+bi is a root, a-bi is also a root
multiplicities are the number of times the root repeats
so root r1 multiplicity 2 would be (x-r1)^2
so therefor
degree 4
roots are 4+3i and 4-3i and 1 twice
(x-(4-3i))(x-(4+3i))(x-1)²
expanding is a pain
used calculator
[tex]f(x)=x^4-10x^3+42x^2-58x+25[/tex]
not sure what the 'a' in front is