# Find all real and complex zeros of h(x)

1. Oct 29, 2013

### FrugalIntelle

1. The problem statement, all variables and given/known data
It's asking me to find all the real and complex zeros of the function x^3 + 2x^2 - 16.

2. Relevant equations

3. The attempt at a solution
I have tried factoring the first 2 terms and i come up with x2(x+2) - 16 but I don't know where to go from there. Any help would be appreciated.

2. Oct 29, 2013

### Staff: Mentor

This is not really a very good start. Instead you should see if you can find a number r such that x3 + 2x2 - 16 = (x - r) * (x2 + lower degree terms).

The Rational Root Theorem (you can search for this on the web) says that if r is a root of your cubic polynomial, it has to be a number that evenly divides -16. The only candidates are ±1, ±2, ±4, ±8, and ±16. Does your textbook mention this theorem? Does your textbook show any examples of similar problems? Do you read your textbook?

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