Math Problem Statement

Graph the following polynomial function and list its characteristics: f(x) = (x - 4)(x + 1)^2(2x - 1)

Solution

I can help you analyze this polynomial function from the image you've uploaded. Let's go step by step through the information you provided.

The polynomial function given is:

f(x)=(x4)(x+1)2(2x1)f(x) = (x - 4)(x + 1)^2(2x - 1)

Now, I'll work through the different parts:

a. Graph the function:

From the sketch, the function seems to have a behavior typical of a polynomial of degree 4. It crosses the x-axis at x=4x = 4, x=1x = -1, and x=12x = \frac{1}{2} (based on the roots). The graph also appears to show that the function is increasing towards infinity at both extremes.

b. Degree:

The degree of the polynomial is 4. This is because the highest power of xx would come from multiplying the terms:

(x4)(x+1)2(2x1)(x-4)(x+1)^2(2x-1)

Expanding the terms would lead to x4x^4.

c. Sign - Leading coefficient:

The leading coefficient is positive. This is because the highest degree term x4x^4 comes from multiplying the 2x2x in the (2x1)(2x-1) factor, which is positive. Therefore, the graph opens upwards.

d. Type of Function:

Since the degree is 4 (an even number), this is an even-degree polynomial.

e. Quadrants:

The graph appears to cross the y-axis at y=4y = 4 and seems to lie mainly in quadrants II (Q2) and I (Q1).

f. Roots/zeros:

The roots of the function occur where the function equals zero:

  • x=4x = 4
  • x=1x = -1 (with multiplicity 2, meaning the graph will touch the x-axis but not cross it)
  • x=12x = \frac{1}{2}

g. Y-intercepts:

The y-intercept occurs when x=0x = 0. Plugging x=0x = 0 into the equation:

f(0)=(04)(0+1)2(2(0)1)=(4)(1)(1)=4f(0) = (0 - 4)(0 + 1)^2(2(0) - 1) = (-4)(1)(-1) = 4

Thus, the y-intercept is y=4y = 4.

h. Domain:

The domain of any polynomial function is all real numbers: Domain: xR\text{Domain: } x \in \mathbb{R}

i. Range:

Since this is a degree 4 polynomial with a positive leading coefficient, the graph tends to infinity as xx goes to both positive and negative infinity. Therefore, the range is also all real numbers: Range: yR\text{Range: } y \in \mathbb{R}

j. End Behaviors:

As xx \to \infty, f(x)f(x) \to \infty, and as xx \to -\infty, f(x)f(x) \to \infty, because the graph opens upwards.

k. Local Maximums and Minimums:

This part involves identifying turning points from the graph. It seems from the sketch that there may be a local minimum near x=1x = 1 and a local maximum near x=2x = -2, but this is not confirmed in the graph. Calculating derivatives would help find these points exactly.

l. Interval of Positive & Negative of the Function:

The function is negative between the roots x=4x = 4 and x=12x = \frac{1}{2} and positive otherwise. Based on the roots:

  • Positive when x(,1)(12,4)x \in (-\infty, -1) \cup (\frac{1}{2}, 4)
  • Negative when x(1,12)x \in (-1, \frac{1}{2})

m. Interval of Increase & Decrease of the Function:

This can be determined by analyzing the first derivative, but visually, the function increases in intervals (,1)(1/2,)(-\infty, -1) \cup (1/2, \infty) and decreases between (1,1/2)(-1, 1/2).


Would you like me to calculate any of these features in more detail, such as finding the exact turning points?

Relative Questions:

  1. How do you find the multiplicity of a root in a polynomial?
  2. What impact does the leading coefficient have on the shape of the graph?
  3. How can you verify the intervals of increase and decrease mathematically?
  4. What determines whether a polynomial function has a maximum or minimum?
  5. Why do even-degree polynomials generally open upwards or downwards?

Tip:

Always analyze the multiplicity of the roots carefully, as it tells you whether the graph will cross or just touch the x-axis at that root.

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Math Problem Analysis

Mathematical Concepts

Polynomial Functions
Roots/Zeros of Polynomial
Graphing Polynomial Functions
End Behavior

Formulas

f(x) = (x - 4)(x + 1)^2(2x - 1)
Leading term from expansion: 2x^4

Theorems

Fundamental Theorem of Algebra
Multiplicity of roots

Suitable Grade Level

Grades 11-12