Which are real zeroes of this function?
x^3 + 2x^2 – 9x – 18

Question

Which are real zeroes of this function?
x^3 + 2x^2 – 9x – 18

imstuck · Answer

Are you familiar with the Rational Roots theroem?

imstuck · Answer

The idea behind the rations roots theorem is to find the first factor of your polynomial.  Do this by finding all the factors of both the first constant that the last.  The first constant is a 1, so the only options for multiples for 1 is plus/minus 1.  For the 18, your options are +/-1, +/-2, +/-3, +/-6. +/-9, +/-18

imstuck · Answer

Using synthetic division, find the first real root if it exists.  Do this by using all your multiples you listed above and find which one leaves a 0 remainder.  Like this:

imstuck · Answer

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