Chapter 9: Problem 6
Identify the vertex of each parabola. $$ f(x)=-4 x^{2} $$
Short Answer
Expert verified
The vertex of the parabola is \( (0, 0) \).
Step by step solution
01
Identify the general form of the quadratic function
A quadratic function is typically written in the form \[ f(x) = ax^2 + bx + c \]. In this case, the given function is \[ f(x) = -4x^2 \], which means \[ a = -4 \], \[ b = 0 \], and \[ c = 0 \].
02
Understand the vertex form of a parabola
The vertex of a parabola given by a quadratic function in the general form \[ y = ax^2 + bx + c \] can be found using the formula \[ x = -\frac{b}{2a} \] to find the x-coordinate.
03
Calculate the x-coordinate of the vertex
Use \[ x = -\frac{b}{2a} \] and substitute \[ b = 0 \] and \[ a = -4 \]. Therefore, \[ x = -\frac{0}{2(-4)} = 0 \].So, the x-coordinate of the vertex is \[ x = 0 \].
04
Determine the y-coordinate of the vertex
Substitute \[ x = 0 \] back into the original function to find the y-coordinate. \[ f(0) = -4(0)^2 = 0 \].So, the y-coordinate of the vertex is \[ y = 0 \].
05
Combine the coordinates to find the vertex
The vertex of the parabola is the point where \[ x = 0 \] and \[ y = 0 \]. Therefore, the vertex is \[ (0, 0) \].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
quadratic function
A quadratic function is one of the simplest types of polynomial functions. It's typically expressed in the form \( f(x) = ax^2 + bx + c \). Each term in the equation corresponds to a specific part of the parabola it represents.
This results in a downward-opening parabola where the vertex will play a key role in understanding its graph.
- \(a\): This coefficient controls the direction and width of the parabola. If \(a\) is positive, the parabola opens upwards. If \(a\) is negative, it opens downwards. A larger absolute value of \(a\) makes the parabola narrower.
- \(b\): This coefficient affects the location of the vertex and the symmetry of the parabola.
- \(c\): This is the y-intercept, showing where the parabola crosses the y-axis.
This results in a downward-opening parabola where the vertex will play a key role in understanding its graph.
vertex formula
The vertex of a parabola, or the highest or lowest point on its graph, is a crucial feature. To find the vertex from a quadratic function, we use the vertex formula. Here’s how it works:
1. Calculate the x-coordinate: \( x = -\frac{b}{2a} = -\frac{0}{2(-4)} = 0 \).2. Find the y-coordinate by substituting \( x = 0 \) back into the function: \( f(0) = -4(0)^2 = 0 \).
So, the vertex is at \( (0, 0) \), meaning the parabola touches the origin.
- The x-coordinate of the vertex can be found using the formula: \( x = -\frac{b}{2a} \). This is derived from completing the square or using calculus.
- After finding the x-coordinate, substitute it back into the original function \( f(x) \) to find the y-coordinate.
1. Calculate the x-coordinate: \( x = -\frac{b}{2a} = -\frac{0}{2(-4)} = 0 \).2. Find the y-coordinate by substituting \( x = 0 \) back into the function: \( f(0) = -4(0)^2 = 0 \).
So, the vertex is at \( (0, 0) \), meaning the parabola touches the origin.
parabolic functions
Parabolic functions, often represented by quadratic equations, are a fundamental concept in algebra and calculus. They form U-shaped curves called parabolas. Here are key characteristics of parabolic functions:
- Symmetry: Parabolas are symmetric around a vertical line called the axis of symmetry, which passes through the vertex.
- Vertex: The highest or lowest point of the parabola. This can be a maximum (if the parabola opens downwards) or a minimum (if it opens upwards).
- Direction: Determined by the sign of the coefficient \( a \). Positive opens up, negative opens down.