How do you find the number of possible positive real zeros and negative zeros then determine the rational zeros given f(x)=x3−2x2−8x?
1 Answer
The zeros of
Explanation:
Given:
f(x)=x3−2x2−8x
Note that the signs of the coefficients of
The signs of the coefficients of
In order to usefully apply the rational zeros theorem we need a non-zero constant term, but
x3−2x2−8x=x(x2−2x−8)
Now applying the rational zeros theorem to
That means that its only possible rational zeros are:
±1,±2,±4,±8
Trying these, we find:
(−2)2−2(−2)−8=4+4−8=0
(4)2−2(4)−8=16−8−8=0
So the zeros of