posted by Brent .
find all zeros, write polynomial as product of linear factors
1) f(x)=9x^3 - x^2 +9x -9
2) f(x)=x^4 -21x^2 -100
3) f(x)=x^3 -3x^2 -5x +39
#1 There must be a typo here. Not factorable
now it should be easy
#3 a little tinkering shows that you have
again, complex roots.