# How to write a polynomial function with given complex zeros

Think of a polynomial graph of higher degrees degree at least 3 as quadratic graphs, but with more twists and turns. The same is true with higher order polynomials. If we can factor polynomials, we want to set each factor with a variable in it to 0, and solve for the variable to get the roots. This is because any factor that becomes 0 makes the whole expression 0.

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That is the topic of this section. In general, finding all the zeroes of any polynomial is a fairly difficult process. In this section we will give a process that will find all rational i.

We will be able to use the process for finding all the zeroes of a polynomial provided all but at most two of the zeroes are rational. If more than two of the zeroes are not rational then this process will not find all of the zeroes. We will need the following theorem to get us started on this process.

Note that in order for this theorem to work then the zero must be reduced to lowest terms. Example 1 Verify that the roots of the following polynomial satisfy the rational root theorem. Also, with the negative zero we can put the negative onto the numerator or denominator. So, according to the rational root theorem the numerators of these fractions with or without the minus sign on the third zero must all be factors of 40 and the denominators must all be factors of Here are several ways to factor 40 and Also note that, as shown, we can put the minus sign on the third zero on either the numerator or the denominator and it will still be a factor of the appropriate number.

So, why is this theorem so useful? Well, for starters it will allow us to write down a list of possible rational zeroes for a polynomial and more importantly, any rational zeroes of a polynomial WILL be in this list.

In other words, we can quickly determine all the rational zeroes of a polynomial simply by checking all the numbers in our list. Example 2 Find a list of all possible rational zeroes for each of the following polynomials.

So, the first thing to do is actually to list all possible factors of 1 and 6. This is actually easier than it might at first appear to be. There is a very simple shorthanded way of doing this. There are four fractions here. This will always happen with these kinds of fractions.

First get a list of all factors of -9 and 2. Here then is a list of all possible rational zeroes of this polynomial. The following fact will also be useful on occasion in finding the zeroes of a polynomial.

What this fact is telling us is that if we evaluate the polynomial at two points and one of the evaluations gives a positive value i. Also, note that if both evaluations are positive or both evaluations are negative there may or may not be a zero between them.

Here is the process for determining all the rational zeroes of a polynomial. Evaluate the polynomial at the numbers from the first step until we find a zero. This repeating will continue until we reach a second degree polynomial.The zeroes of the function (and, yes, "zeroes" is the correct way to spell the plural of "zero") are the solutions of the linear factors they've given me.

Solving each factor gives me: x + 5 = 0 ⇒ x = –5. Zeros of a Polynomial Function Factor Theorem + Rational Zeros Theorem.

What we are going to explore throughout this lesson is how to find all other zeros of a polynomial function given one zero. Algebra II, Chapter 5. STUDY. PLAY. Write each polynomial in standard form. Then classify by degree and number of terms. Write a polynomial function in standard form with the given zeros.

Use the zeros of a polynomial to write a polynomial as a product of linear and irreducible quadratic factors. First you should become familiar with the following theorems and concepts Fundamental Theorem of Algebra (NEW): A polynomial function of degree n > 0 has n complex zeros.

Construct a polynomial function with the given graph. Ask Question. up vote 3 down vote favorite.

Given the window, we may as well assume these are the only zeros of the polynomial. Note also that we don't have any "flattening" near the zeros, so the zeros must be of multiplicity \$1\$.

Seeing complex roots on the graph of a polynomial. 0. write a polynomial function of least degree that has real coefficeints the given zeros and a leading coefficient of 1.

the problem is 5,2i,-2i asked by jay on October 14, Algebra 2.

Algebra - Finding Zeroes of Polynomials