9514 1404 393
Answer:
- zeros: {-2, -1, 7}
- P(x) = (x +2)(x +1)(x -7)
Step-by-step explanation:
Descarte's rule of signs tells you there is 1 positive real root. The rational root theorem tells you any real roots are factors of ±14, so will be ±1, ±2, ±7, or ±14.
We note that the sum of all coefficients is negative, so +1 is not a root.
We note that the sum of coefficients of odd-degree terms is 1-19 = -18, and the sum of coefficients of even-dgree terms is -4-14 = -18. These are the same value, indicating that -1 is a root. The corresponding factor is (x +1).
The result of dividing the factor (x+1) from the polynomial using synthetic division is shown in the first attachment. The coefficients found mean the quotient is ...
Q(x) = x^2 -5x -14
Factoring this using any method you like gives ...
Q(x) = (x +2)(x -7)
This means the full set of zeros is {-2, -1, +7} and the factorization is ...
P(x) = (x +2)(x +1)(x -7)
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Additional comment
My personal favorite method of finding the zeros is to let a graphing calculator show them to me. That result is shown in the second attachment.
