College Algebra : Polynomial Functions

Study concepts, example questions & explanations for College Algebra

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Example Questions

Example Question #51 : Polynomial Functions

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Example Question #51 : Polynomial Functions

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Example Question #51 : Polynomial Functions

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Example Question #231 : College Algebra

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Example Question #31 : Zeros/Roots Of A Polynomial

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Example Question #233 : College Algebra

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Example Question #52 : Polynomial Functions

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Example Question #231 : College Algebra

Consider the polynomial

Which of the following is true of the rational zeroes of  ?

Hint: Think "Rational Zeroes Theorem".

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There are no rational zeroes.

 is the only rational zero. 

1 is the only rational zero.

Neither  nor 1 is a rational zero, but there is at least one rational zero.

 and 1 are the only rational zeroes.

Correct answer:

1 is the only rational zero.

Explanation:

By the Rational Zeroes Theorem, any rational zeroes of a polynomial must be obtainable by dividing a factor of the constant coefficient by a factor of the leading coefficient. Since both values are equal to 1, and 1 has only 1 as a factor, this restricts the set of possible rational zeroes to the set .

1 is a zero of  if and only if . An easy test for this is to add the coefficients and determine whether their sum, which is , is 0:

1 is a zero.

 is a zero of  if and only if . An easy test for this is to add the coefficients after changing the sign of the odd-degree coefficients, and determine whether their sum, which is , is 0:

 is not a zero.

1 is the only rational zero.

Example Question #236 : College Algebra

The polynomial

has a zero on one of the following intervals. Which one?

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The Intermediate value Theorem states that if  is a continuous function, , and  and  are of unlike sign, it must hold that  for some . Equivalently, if  has values on the endpoints of an interval that differ in sign, then  has a zero on that interval. Since all polynomial functions are continuous, we may apply this theorem by evaluating  

for , and finding two consecutive values such that  differs in sign.

By substitution, we can find that:

The change in sign occurs on the interval ; therefore, a zero of  is located on this interval.

Example Question #232 : College Algebra

Consider the polynomial

.

The Rational Zeroes Theorem allows us to reduce the possible rational zeroes of this polynomial to a set comprising how many elements?

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Explanation:

By the Rational Zeroes Theorem, any rational zero of a polynomial with integer coefficients must be equal to a factor of the constant divided by a factor of the leading coefficient, taking both positive and negative numbers into account.

The constant 17, being prime, has only two factors, 1 and 17; the leading coefficient is 1, which only has 1 as a factor. Thus, the only possible rational zeroes of the given polynomial are given in the set

,

a set of four elements. This makes 4 the correct choice.

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