Answer:
x=3 and x=-1
Explanation:
Given Descartes' Rule of Signs, there is only one positive root and one negative root.
The Rational Root Theorem states that if a polynomial zeroes for a rational number P/Q then P is a factor of the Trailing Constant and Q is a factor of the Leading Coefficient.
So P could be +1, -1, +3, or -3, while Q could be 1 or -1.
Therefore, P/Q could be +1, -1, +3, or -3.
Then we use synthetic division to find the correct factor(s):
1 | 1 -1 -5 -3
___ 1_0_ -5
1 0 -5 | -8
So (x-1) is not a factor
-1 | 1 -1 -5 -3
___-1_2_ 3
1 -2 -3 | 0
So (x+1) is a factor where the quotient is x^2-2x-3 or (x-3)(x+1)
3 | 1 -1 -5 -3
___ 3_6_ 3
1 2 1 | 0
So (x-3) is a factor where the quotient is x^2+2x+1 or (x+1)^2
Given (x-3) and (x+1) are factors, we now use the Zero Product Property:
(x-3)(x+1)=0
x-3=0
x=3
x+1=0
x=-1
So the roots are x=3 and x=-1