Prove Root of Polynomial $P(x)=x^{13}+x^7-x-1$ Has 1 Positive Zero

In summary, a positive zero is a value that, when substituted into a polynomial, results in an output of zero. The polynomial $P(x)$ has at most one positive zero, which can be proven by showing that there exists a value of $x$ that, when substituted into the polynomial, results in an output of zero. The rational root theorem cannot be used to find the positive zero of $P(x)$, as it only applies to polynomials with integer coefficients. Proving that $P(x)$ has a positive zero is significant because it can help us understand the behavior and properties of the polynomial near that zero, aiding in graphing and analysis.
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Prove that the polynomial $P(x)=x^{13}+x^7-x-1$ has only one positive zero.
 
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  • #2
P(x) has one change of sign. so there is 1 positive root or number of positive roots (1 -2n) as per Descartes' rule of signs. so number of positive roots is one
 
  • #3
$P(x)=x^{13}+x^7−x−1$
$= x(x^{12}-1) +x^7-1$
$=(x-1)(x(x^{11}+ x^{10} + \cdots 1)+ (x-1)(x^6+x^5+\cdots + 1))$
$= (x-1)( x(x^{11}+ x^{10} + \cdots 1) + (x^6+x^5+\cdots + 1))$
1st term is x -1 and 2nd term is positive for positive x . so x = 1 is the only solution
 

FAQ: Prove Root of Polynomial $P(x)=x^{13}+x^7-x-1$ Has 1 Positive Zero

What is the definition of a positive zero of a polynomial?

A positive zero of a polynomial is a value of x that makes the polynomial equal to zero when plugged in for x. In other words, it is a value that satisfies the equation P(x) = 0 and is greater than 0.

How do you prove that a polynomial has a positive zero?

To prove that a polynomial has a positive zero, we can use the Intermediate Value Theorem. This theorem states that if a continuous function has values of opposite signs at two points, then there exists at least one root between those two points. In the case of the polynomial P(x), we can show that P(0) = -1 and P(1) = 1, which means there must be at least one positive zero between 0 and 1.

Why is it important to prove that a polynomial has a positive zero?

Proving that a polynomial has a positive zero is important because it allows us to find the roots of the polynomial, which can provide valuable information about the behavior and characteristics of the polynomial. Additionally, it can help us solve equations and make predictions in various fields such as physics, engineering, and economics.

What is the significance of the polynomial P(x)=x^{13}+x^7-x-1 having 1 positive zero?

The significance of the polynomial P(x)=x^{13}+x^7-x-1 having 1 positive zero is that it tells us that there is at least one value of x that makes the polynomial equal to zero. This means that the polynomial has at least one real root, which can be useful in solving equations and understanding the behavior of the polynomial.

Can a polynomial have more than one positive zero?

Yes, a polynomial can have more than one positive zero. In fact, the polynomial P(x)=x^{13}+x^7-x-1 has exactly one positive zero, but it also has other roots that are not positive. This is because polynomials can have complex roots, which are not real numbers. However, the converse is not true - a polynomial cannot have more positive zeros than its degree.

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