Chapter 11: Problem 62
Is it possible for the graph of a quadratic function to have only one \(x\) -intercept if the vertex is off the \(x\) -axis? Why or why not?
Short Answer
Expert verified
No, a quadratic function's graph cannot have only one x-intercept if the vertex is off the x-axis.
Step by step solution
01
- Understand the problem
Identify the key elements of the problem: a quadratic function graphed on the Cartesian plane and its potential number of x-intercepts.
02
- Recall the properties of a quadratic function
A quadratic function is generally in the form of \( f(x) = ax^2 + bx + c \). The graph of such a function is a parabola, which can intersect the x-axis at 0, 1, or 2 points.
03
- Define the vertex of a quadratic function
The vertex of a parabola given by \( f(x) = ax^2 + bx + c \) is at the point \( (h, k) \), where \( h = -\frac{b}{2a} \) and \( k = f(h) \).
04
- Consider the vertex position relative to the x-axis
The problem states that the vertex is off the x-axis, meaning \( k eq 0 \).
05
- Analyze the number of x-intercepts
For the parabola to have exactly one x-intercept, the vertex must lie on the x-axis (\( k = 0 \)). If the vertex is not on the x-axis (\( k eq 0 \)), the parabola can either intersect the x-axis at two points or not intersect at all, depending on whether \( ax^2 \) opens upwards or downwards.
06
- Conclusion
If the vertex is off the x-axis (\( k eq 0 \)), it is impossible for the parabola to have exactly one x-intercept.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
quadratic functions
A quadratic function is a specific type of polynomial function with the general form \( f(x) = ax^2 + bx + c \), where \( a, b, \) and \( c \) are constants and \( a eq 0 \). The graph of a quadratic function is a curve called a parabola. The parabola can open upwards (if \( a > 0\)) or downwards (if \( a < 0\)).
Key characteristics of quadratic functions include:
Key characteristics of quadratic functions include:
- **Vertex:** This is the highest or lowest point on the graph, depending on the parabola's direction.
- **Axis of symmetry:** A vertical line through the vertex, given by \( x = h \), divides the parabola into two symmetrical halves.
- **X-intercepts:** Points where the graph intersects the x-axis.
- **Y-intercept:** The point where the graph intersects the y-axis (where \( x = 0 \)).
parabola vertex
The vertex of a parabola is a crucial point where the graph changes direction. For a quadratic function \( f(x) = ax^2 + bx + c \), the vertex is located at the point \( (h, k) \).
Here's how you can find the vertex:
If the vertex is located on the x-axis, it means \( k = 0 \). This condition is essential when considering the number of x-intercepts a parabola can have.
Here's how you can find the vertex:
- First, calculate \( h \) using the formula \( h = -\frac{b}{2a} \).
- Then, find \( k \) by substituting \( h \) back into the function: \( k = f(h) \).
If the vertex is located on the x-axis, it means \( k = 0 \). This condition is essential when considering the number of x-intercepts a parabola can have.
x-intercepts
X-intercepts are the points at which the graph of the quadratic function crosses the x-axis. These are also known as the 'roots' or 'zeroes' of the function. To find the x-intercepts of a quadratic function \( f(x) = ax^2 + bx + c \), solve the equation \( ax^2 + bx + c = 0 \).
There are three possible scenarios:
There are three possible scenarios:
- The parabola has **two distinct x-intercepts** if the discriminant \( b^2 - 4ac \) is greater than 0.
- The parabola has **one x-intercept** (it touches the x-axis at one point) if the discriminant is equal to 0. This can only happen when the vertex is on the x-axis.
- The parabola has **no x-intercepts** if the discriminant is less than 0.