High School

Use the Rational Root Theorem to find the list of all potential rational solutions to the equation:

[tex]3x^5 - 10x^4 + 12x^3 - 15x^2 + 25x - 35 = 0[/tex]

A. [tex]\pm \frac{1}{35}, \pm \frac{1}{7}, \pm \frac{1}{5}, \pm \frac{3}{35}, \pm \frac{3}{7}, \pm \frac{3}{5}, \pm 1, \pm 3[/tex]

B. [tex]\pm \frac{1}{3}, \pm \frac{1}{10}, \pm \frac{1}{12}, \pm \frac{1}{15}, \pm \frac{1}{25}, \pm \frac{1}{35}[/tex]

C. [tex]\pm 35, \pm 7, \pm 5, \pm 1, \pm \frac{35}{3}, \pm \frac{7}{3}, \pm \frac{5}{3}, \pm \frac{1}{3}[/tex]

D. The polynomial has no rational roots

E. [tex]\pm 3, \pm 10, \pm 12, \pm 15, \pm 25, \pm 35[/tex]

Answer :

To find the possible rational roots of

[tex]$$3x^5 - 10x^4 + 12x^3 - 15x^2 + 25x - 35 = 0,$$[/tex]

we can use the Rational Root Theorem. This theorem tells us that any rational solution (root) of the polynomial equation can be written in the form

[tex]$$x = \pm \frac{p}{q},$$[/tex]

where

- [tex]$p$[/tex] is a factor of the constant term, and
- [tex]$q$[/tex] is a factor of the leading coefficient.

Let’s work through this step by step.

1. Identify the Constant and Leading Coefficient

- The constant term is [tex]$-35$[/tex]. Its factors (ignoring the sign) are:

[tex]$$1,\, 5,\, 7,\, 35.$$[/tex]

- The leading coefficient is [tex]$3$[/tex]. Its factors (ignoring the sign) are:

[tex]$$1,\, 3.$$[/tex]

2. List the Possible Values for [tex]$x$[/tex]

According to the theorem, the candidate rational roots are given by

[tex]$$x = \pm \frac{p}{q},$$[/tex]

where [tex]$p \in \{1, 5, 7, 35\}$[/tex] and [tex]$q \in \{1, 3\}$[/tex]. This gives the following list of potential rational roots:

[tex]$$\begin{array}{cccc}
\pm \frac{1}{1}, & \pm \frac{5}{1}, & \pm \frac{7}{1}, & \pm \frac{35}{1},\\[1mm]
\pm \frac{1}{3}, & \pm \frac{5}{3}, & \pm \frac{7}{3}, & \pm \frac{35}{3}.
\end{array}$$[/tex]

3. Write the Final List in a Clear Format

Arranging the factors, the potential rational solutions are:

[tex]$$\pm 1, \quad \pm 5, \quad \pm 7, \quad \pm 35, \quad \pm \frac{1}{3}, \quad \pm \frac{5}{3}, \quad \pm \frac{7}{3}, \quad \pm \frac{35}{3}.$$[/tex]

4. Sorting by Absolute Value (Optional)

Sometimes, it is helpful to list the roots in order of increasing absolute value. When sorted by the absolute value, the list becomes:

[tex]$$\pm \frac{1}{3}, \quad \pm 1, \quad \pm \frac{5}{3}, \quad \pm 5, \quad \pm \frac{7}{3}, \quad \pm 7, \quad \pm \frac{35}{3}, \quad \pm 35.$$[/tex]

This is the complete set of potential rational roots determined by the Rational Root Theorem.

Thus, the list of all potential rational solutions to the equation

[tex]$$3x^5 - 10x^4 + 12x^3 - 15x^2 + 25x - 35 = 0$$[/tex]

is

[tex]$$\boxed{\pm \frac{1}{3}, \; \pm 1, \; \pm \frac{5}{3}, \; \pm 5, \; \pm \frac{7}{3}, \; \pm 7, \; \pm \frac{35}{3}, \; \pm 35.}$$[/tex]