Question

How do I write a polynomial when given the zeros​

Answer 1

Answer:

Subtract the first zero from x and enclose it in parentheses. This is the first factor. For example if a polynomial has a zero that is -1, the corresponding factor is x - (-1) = x + 1.

Raise the factor to the power of the multiplicity. For instance, if the zero -1 in the example has a multiplicity of two, write the factor as (x +1)^2.

Repeat Steps 1 and 2 with the other zeros and add them as further factors. For instance, if the example polynomial has two more zeros, -2 and 3, both with multiplicity 1, two more factors -- (x +2) and (x -3) -- must be added to the polynomial. The final form of the polynomial is then ((x +1)^2)(x +2)(x -3).

Multiply out all the factors using the FOIL (First Outer Inner Last) method to get the polynomial in the standard form. In the example, first multiply (x + 2)(x - 3) to get x^2 + 2x - 3x - 6 = x^2 - x - 6. Then multiply this with another factor (x + 1) to get (x^2 - x - 6)(x + 1) = x^3 +x^2 - x^2 - x - 6x - 6 = x^3 - 7x - 6. Finally, multiply this with the last factor (x + 1) to get (x^3 - 7x - 6)(x + 1) =x^4+x^3-7x^2-7x-6x-6 = x^4 + x^3 - 7x^2 - 13x - 6. This is the standard form of the polynomial.

Answer 2

Given the zeros of a polynomial, you can very easily write it -- first in its factored form and then in the standard form. Subtract the first zero from x and enclose it in parentheses. This is the first factor. For example if a polynomial has a zero that is -1, the corresponding factor is x - (-1) = x + 1.