Polynomial Functions - College Algebra

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Question

Consider the polynomial

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

Hint: Think "Rational Zeroes Theorem".

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Answer

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.

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