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Graphing Factored Polynomials Sketch the graph of the polynomial function. Make sure your graph shows all intercepts and exhibits the proper end behavior. $$P(x)=(2-x)(x+5)$$

Short Answer

Expert verified
The graph has x-intercepts at 2 and -5, y-intercept at 10, and falls on both ends.

Step by step solution

01

Identify the Factors

First, write down the factors of the polynomial function: The polynomial is given as \( P(x) = (2-x)(x+5) \). These factors are \( (2-x) \) and \( (x+5) \). We will use these factors to find the intercepts.
02

Find the X-Intercepts

Set each factor equal to zero to find the x-intercepts.\[(2-x) = 0\] and \[(x+5)=0\] Solving these gives the x-intercepts: \( x = 2 \) and \( x = -5 \). This means the graph passes through these points on the x-axis.
03

Find the Y-Intercept

To find the y-intercept, set \( x = 0 \) in the polynomial. \[ P(0) = (2-0)(0+5) = 2 \times 5 = 10 \] Thus, the y-intercept is 10. The graph crosses the y-axis at (0,10).
04

Determine the End Behavior

Since the leading term of the polynomial as \( x \) tends to infinity is \( -x^2 \) (because when expanded, \( 2x \times x = -1x^2 \)), the polynomial's end behavior is determined by this negative leading coefficient. As \( x \to \pm \infty \), \( P(x) \to -\infty \). Thus, the graph will fall on both ends.
05

Sketch the Graph

Now, plot the x and y-intercepts on a graph first. You have x-intercepts at \( x = 2 \) and \( x = -5 \), and a y-intercept at \( y = 10 \). Then, draw the curve passing through these points ensuring the graph falls on both ends according to the end behavior, passing through the intercept points in a smooth curve.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

x-intercepts
An x-intercept of a polynomial function is a point on the graph where the curve crosses the x-axis. At these points, the y-value is zero because the graph is exactly at the level of the x-axis. To determine the x-intercepts of a factored polynomial, such as \( P(x) = (2-x)(x+5) \), we can set each factor equal to zero and solve for \( x \). This is because a product is zero only if at least one of its factors is zero.
For the given polynomial, the factors are \( (2-x) \) and \( (x+5) \).
  • Setting \( 2-x = 0 \) gives \( x = 2 \).
  • Setting \( x+5 = 0 \) gives \( x = -5 \).
Hence, the x-intercepts are at \( x = 2 \) and \( x = -5 \). These points mean that the graph passes through \( (2, 0) \) and \( (-5, 0) \), forming crucial parts of the graph's structure.
y-intercept
The y-intercept is where the graph crosses the y-axis, and it's determined by evaluating the function at \( x = 0 \). This value tells us where the polynomial will intersect the y-axis, giving insight into how the graph behaves in the vicinity of the origin.
For the polynomial \( P(x) = (2-x)(x+5) \), substitute \( x = 0 \) into the expression.
  • Calculate \( P(0) = (2-0)(0+5) = 2 \times 5 = 10 \).
Thus, the y-intercept is the point \( (0, 10) \) on the graph. Knowing this helps in plotting the graph accurately, especially when combined with x-intercepts, as it anchors the graph on the y-axis.
end behavior
End behavior in polynomials refers to what happens to the function's values as \( x \) approaches positive or negative infinity. For a more accurate sketch of the graph, understanding end behavior ensures that we know how the graph behaves "at the edges."
The given polynomial \( P(x) = (2-x)(x+5) \) can be expanded to give a leading term. When expanded, \( (2-x)(x+5) = -x^2 + 10 \) (ignoring lower degree terms for end behavior). The dominant term is \( -x^2 \), meaning as \( x \) moves towards infinity or minus infinity, \( P(x) \) heads towards negative infinity. This tells us that:
  • As \( x \to +\infty \), \( P(x) \to -\infty \).
  • As \( x \to -\infty \), \( P(x) \to -\infty \).
Essentially, the graph falls (heads downwards) at both ends, indicating a "downward" direction on both sides of the graph.
graph sketching
Graph sketching is about visually representing a polynomial function on a coordinate plane. It involves plotting the intercepts and considering the end behavior to complete the picture.
To sketch \( P(x) = (2-x)(x+5) \), start by plotting the intercepts identified earlier:
  • X-intercepts at \( (2, 0) \) and \( (-5, 0) \).
  • Y-intercept at \( (0, 10) \).
Once these points are plotted, the curve should pass smoothly through them, respecting the end behavior which indicates that both ends of the graph should fall downwards.
Therefore, connect the intercepts with a smooth curve, ensuring the graph falls as \( x \to \pm \infty \). The careful specification of these attributes results in a more accurate and clear visual representation of the polynomial function.

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Most popular questions from this chapter

A baseball team plays in a stadium that holds \(55,000\) spectators. With the ticket price at \(\$ 10,\) the average attendance at recent games has been \(27,000 .\) A market survey indicates that for every dollar the ticket price is lowered, attendance increases by 3000 . (a) Find a function that models the revenue in terms of ticket price. (b) Find the price that maximizes revenue from ticket sales. (c) What ticket price is so high that no revenue is generated?

Solve the inequality $$(x-a)(x-b)(x-c)(x-d) \geq 0$$ where \(a < b < c < d\).

Graph the rational function, and find all vertical asymptotes, \(x\) - and \(y\) -intercepts, and local extrema, correct to the nearest tenth. Then use long division to find a polynomial that has the same end behavior as the rational function, and graph both functions in a sufficiently large viewing rectangle to verify that the end behaviors of the polynomial and the rational function are the same. $$y=\frac{x^{4}-3 x^{3}+x^{2}-3 x+3}{x^{2}-3 x}$$g

Find the factors that are common in the numerator and the denominator. Then find the intercepts and asymptotes, and sketch a graph of the rational function. State the domain and range of the function. $$r(x)=\frac{x^{2}+4 x-5}{x^{3}+7 x^{2}+10 x}$$

Graph the rational function \(f\), and determine all vertical asymptotes from your graph. Then graph \(f\) and \(g\) in a sufficiently large viewing rectangle to show that they have the same end behavior. $$f(x)=\frac{-x^{3}+6 x^{2}-5}{x^{2}-2 x}, \quad g(x)=-x+4$$

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