Chapter 3: Problem 16
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 \( (x+5) \).
For the given polynomial, the factors are \( (2-x) \) and \( (x+5) \).
- Setting \( 2-x = 0 \) gives \( x = 2 \).
- Setting \( x+5 = 0 \) gives \( x = -5 \).
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.
For the polynomial \( P(x) = (2-x)(x+5) \), substitute \( x = 0 \) into the expression.
- Calculate \( P(0) = (2-0)(0+5) = 2 \times 5 = 10 \).
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:
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 \( x \to -\infty \), \( P(x) \to -\infty \).
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:
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.
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 \( (0, 10) \).
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.