Question 112257
if 1+3i is a zero (root) then (x-1-3i) is a factor


since complex roots occur in conjugate pairs, (x-1+3i) is also a factor


so (x-1-3i)(x-1+3i) or x^2-2x+10 is a factor


(x^4-2x^3+5x^2+10x-50)/(x^2-2x+10)=x^2-5


this gives (x+sqrt(5)) and (x-sqrt(5)) as the two other factors