x^5-5x^3+4x
...I don't know exactly how to do that :-|
Or.
Take the possible zero's using the rational rooth theorem.
1.Then used synthetic division a few times.
2.Once done, you will have found all the zero's (where r=0).
3.Then just put it in factored form.
1.
1) 1,0,-5,0,4
-1) 1,1,-4,-4
2) 1,0,-4,0
-2) 1,2,0,0
3.Now look at the coefficients left.
1,0,0,0
subtract leading exponent by number of divisions made::
5-4=1
therefore the coefficient is x.
place the zero's in factored form
multiply by x
Seems harder & longer, but sometimes this method can be a life saver >.> for me at least