Question 538594: How to find rational roots of:
x^3 + 5x^2 - x - 5
I want to know what's the method.
Thank you Answer by KMST(5328) (Show Source):
You can put this solution on YOUR website! If there is a rational root to a polynomial with integer coefficients, the numerator will be a factor of the independent term (-5 in this case), and the denominator will be a factor of the leading coefficient (the invisible +1 multiplying x^3 in this case). So the rational roots will have 1 for a denominator (they are integers). The factors of 5 are 1, and 5, and could appear as roots with a positive or negative sign.
You could just try them.
In this case, this polynomial looks like a factor-by-grouping example:
So it turns out that the 3 roots are all rational, and are -5, -1, and +1.
