Finding the zeros of a Polynomial Function:

Question 1:
A) Choose whole numbers to fill in the two blanks in the following polynomial function:
h(x)=-3x^2 (5x+10)(x-2)

B) Find the zeros of h(x). Show your work.
C)Plot the zeros of h(x) on a coordinate plane on a piece of graph paper. Label this paper Graph 1. Note: You will complete Graph 1 throughout the portfolio. Dont worry about scaling the y-axis at this time.

Question 2:
A) Find the zeros of j(x) =(12x^3)/(5) - (27x)/(5). Show your work.
B) Plot the zeros of j(x) on a coordinate plane on a new piece of graph paper. Label this paper graph 2. Note: You will complete Graph 2 throughout the portfolio. Do not worry about scaling the y-axis at this time.

Sketching Between the Zeros of a Polynomial Function:
Question 1:
A) Refer to the polynomial function h(x) that you wrote in question 1 of Finding the Zeros of a Polynomial Function and find the zeros you located. Choose x-values and determine what the graph of h(x) will look like between its zeros. In particular, make sure to determine whether the graph will be above the x-axis or below the x-axis in each region. Show your work.
B) Find Graph 1 that you started in the first section of this portfolio (on using factored form of a polynomial function to find the zeros of its graph) Using your work from part A, continue the graph of h(x) by scaling the y-axis and sketching what the graph of h(x) looks like between its zeros. Note: You will complete Graph 1 in the final section of the portfolio.

Question 2:
A) Refer to the zeros of j(x) that you found in Question 2 of Finding the Zeros of a Polynomial Function. Choose x-values and determine what the graph of j(x) will look like between its zeros. In particular, make sure to determine whether the graph will be above the x-axis or below the x-axis in each region. Show your work.
B) Find Graph 2 that you started in the first section of this portfolio (on using the factored form of a polynomial function to find the zeros of its graph). Using your work from part A, continue the graph of j(x) by scaling the y-axis and sketching what the graph of j(x) looks like between its zeros. Note: You will complete Graph 2 in the final section of the portfolio.

End Behavior of Polynomial Functions:
Question 1:
A) Refer to the polynomial function h(x) that you wrote in Question 1 of Finding the Zeros of a Polynomial Function. Describe and provide an explanation for the end behavior of h(x).
B) Find Graph 1 that you started in the first section on this portfolio (on using the factored form of a polynomial function to find the zeros of its graph) and continued in the second section of this portfolio (on sketching the portions of polynomial functions graph that exist between its zeros). Using your work from part A, complete the sketch of the graph of h(x) by including its end behavior.

Question 2:
A) Consider j(x). Describe and provide an explanation for the end behavior of j(x)
B) Find Graph 2 that you started in the first section of this portfolio (on using the factored form of a polynomial function to find the zeros of its graph) and continued in the second section of this portfolio (on sketching the portions of a polynomial functions graph that exist between its zeros) using your work from part A, complete the sketch of the graph of j(x) by including its end behavior.

1 answer

Let's tackle the questions step-by-step.

Finding the Zeros of a Polynomial Function:

Question 1:

A)

The polynomial function provided is \( h(x) = -3x^2(5x + 10)(x - 2) \). To fill in the blanks with whole numbers, let's set \( 5x + 10 = 5(x + 2) \).

Thus, the polynomial is: \[ h(x) = -3x^2(5(x + 2))(x - 2) \]

B)

To find the zeros of \( h(x) \), we set \( h(x) = 0 \): \[ -3x^2(5(x + 2))(x - 2) = 0 \]

This equation will be zero if any of the factors are zero:

  1. \( -3x^2 = 0 \)

    • This gives \( x = 0 \).
  2. \( 5(x + 2) = 0 \)

    • This gives \( x + 2 = 0 \) or \( x = -2 \).
  3. \( (x - 2) = 0 \)

    • This gives \( x = 2 \).

The zeros of \( h(x) \) are \( x = 0, -2, 2 \).

Question 2:

A)

For \( j(x) = \frac{12x^3}{5} - \frac{27x}{5} \), factor out the common term: \[ j(x) = \frac{1}{5}(12x^3 - 27x) = \frac{1}{5}(3x(4x^2 - 9)) = \frac{1}{5}(3x(2x - 3)(2x + 3)) \]

Set \( j(x) = 0 \):

  1. \( 3x = 0 \) → \( x = 0 \)
  2. \( 2x - 3 = 0 \) → \( x = \frac{3}{2} \)
  3. \( 2x + 3 = 0 \) → \( x = -\frac{3}{2} \)

The zeros of \( j(x) \) are \( x = 0, \frac{3}{2}, -\frac{3}{2} \).

Sketching Between the Zeros of a Polynomial Function:

Question 1 (for \( h(x) \)):

A)

The zeros found are \( -2, 0, 2 \). The intervals to test are:

  1. \( (-\infty, -2) \)

    • Choose \( x = -3 \) → \( h(-3) = -3(-3)^2(5(-3 + 2))(-3 - 2) = - \) (negative).
  2. \( (-2, 0) \)

    • Choose \( x = -1 \) → \( h(-1) = -3(-1)^2(5(-1 + 2))(-1 - 2) = + \) (positive).
  3. \( (0, 2) \)

    • Choose \( x = 1 \) → \( h(1) = -3(1)^2(5(1 + 2))(1 - 2) = - \) (negative).
  4. \( (2, \infty) \)

    • Choose \( x = 3 \) → \( h(3) = -3(3)^2(5(3 + 2))(3 - 2) = - \) (negative).

So, the behavior is:

  • Above 0 (positive) for \( (-2, 0) \)
  • Below 0 (negative) for other intervals.

B)

On Graph 1, plot points corresponding to the zeros and the behavior found above.

Question 2 (for \( j(x) \)):

A)

The zeros found are \( -\frac{3}{2}, 0, \frac{3}{2} \). The intervals to test are:

  1. \( (-\infty, -\frac{3}{2}) \)

    • Choose \( x = -2 \) → \( j(-2) = \frac{1}{5}(12(-2)^3 - 27(-2)) < 0 \) (negative).
  2. \( (-\frac{3}{2}, 0) \)

    • Choose \( x = -1 \) → \( j(-1) = \frac{1}{5}(12(-1)^3 - 27(-1)) > 0 \) (positive).
  3. \( (0, \frac{3}{2}) \)

    • Choose \( x = 1 \) → \( j(1) = \frac{1}{5}(12(1)^3 - 27(1)) < 0 \) (negative).
  4. \( (\frac{3}{2}, \infty) \)

    • Choose \( x = 2 \) → \( j(2) = \frac{1}{5}(12(2)^3 - 27(2)) > 0 \) (positive).

So, the behavior is:

  • Above 0 (positive) for \( (-\frac{3}{2}, 0) \) and \( (x > \frac{3}{2}) \).

End Behavior of Polynomial Functions:

Question 1 (for \( h(x) \)):

A)

The leading term in \( h(x) = -3x^2(5)(x - 2) \) is \( -15x^3 \).

  • As \( x \to \infty \), \( h(x) \to -\infty \).
  • As \( x \to -\infty \), \( h(x) \to \infty \).

B)

On Graph 1, incorporate the end behavior by extending the lines to reflect this.

Question 2 (for \( j(x) \)):

A)

The leading term is \( \frac{12}{5}x^3 \).

  • As \( x \to \infty \), \( j(x) \to \infty \).
  • As \( x \to -\infty \), \( j(x) \to -\infty \).

B)

On Graph 2, incorporate the end behavior by extending the lines accordingly.

Note:

  1. For both graphing responses, it's essential to accurately represent points and curves to capture the polynomial's behavior visually.
  2. Ensure that all work is clearly noted with labels for clarity when presenting.

This should guide you through completing the assignment effectively!