College Algebra : Finding Zeros of a Polynomial

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Example Questions

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Example Question #261 : College Algebra

Consider the polynomial

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

Hint: Think "Rational Zeroes Theorem".

Possible Answers:

 has at least one rational zero, but neither  nor 1 is a zero.

 has no rational zeroes.

The only rational zero of  is .

The only rational zeroes of  are  and 1.

The only rational zero of  is 1.

Correct answer:

The only rational zeroes of  are  and 1.

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 .

Both values can be tested as follows:

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 indeed 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. However, as their are no odd-degree coefficients, the sum is the same:

 is also a zero.

Example Question #21 : Finding Zeros Of A Polynomial

Determine the zeros of the following equation:  

Possible Answers:

Correct answer:

Explanation:

To determine the zeros of this equation, we will need to factorize the polynomial.

The only common factors of  that will give us a middle term of negative  by addition or subtraction is:

Set each binomial equal to zero and solve.

The zeros are:  

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