Chapter 9: Problem 5
Identify the vertex of each parabola. $$ f(x)=-3 x^{2} $$
Short Answer
Expert verified
The vertex is (0, 0).
Step by step solution
01
Identify the Standard Form of a Parabola
A parabola can be represented in the standard form \( f(x) = ax^2 + bx + c \). In this case, the given function is \( f(x) = -3x^2 \).
02
Coefficients Identification
Identify the values of the coefficients \( a \), \( b \), and \( c \) in the given quadratic function. For \( f(x) = -3x^2 \), \( a = -3 \), \( b = 0 \), and \( c = 0 \).
03
Calculate the Vertex
The vertex of a parabola given by \( y = ax^2 + bx + c \) is located at \( x = -\frac{b}{2a} \). Substitute \( a = -3 \) and \( b = 0 \) into the formula.\[ x = -\frac{0}{2(-3)} = 0 \]
04
Find the y-coordinate
Substitute \( x = 0 \) back into the original equation to find the y-coordinate of the vertex. \[ f(0) = -3(0)^2 = 0 \].
05
State the Vertex
Combine the results. The vertex of the parabola \( f(x) = -3x^2 \) is at the point \( (0, 0) \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
standard form of a parabola
A parabola is a U-shaped curve and its equation can vary slightly in form. To keep things simple, the most common way to write the equation of a parabola is in what is called the standard form. The standard form of a parabola is written as \[ f(x) = ax^2 + bx + c \] Here:
- 'a' controls the width and direction of the parabola. If 'a' is positive, the parabola opens upwards. If 'a' is negative, it opens downwards.
- 'b' influences the position of the vertex along the x-axis.
- 'c' moves the parabola up or down keeping the shape the same.
quadratic function
A quadratic function is a type of polynomial function and it is often written in the form: \[ f(x) = ax^2 + bx + c \] Such functions produce parabolas when graphed. They are called 'quadratic' because 'quadra' means square, and the highest degree (or power) of the variable in the function is a square (\( x^2 \)).
Key points about quadratic functions:
The function \[ f(x) = -3x^2 \] is a quadratic function. Here, 'a' is -3, and since 'b' and 'c' are both 0, it simplifies the function, but this doesn't change the fact that it is a quadratic function.
Key points about quadratic functions:
- They always produce parabolas when graphed.
- They have a squared term as the highest power of the variable.
- The curve can either open upwards or downwards depending on the sign of 'a'.
The function \[ f(x) = -3x^2 \] is a quadratic function. Here, 'a' is -3, and since 'b' and 'c' are both 0, it simplifies the function, but this doesn't change the fact that it is a quadratic function.
vertex calculation
Finding the vertex of a quadratic function \[ f(x) = ax^2 + bx + c \] is essential, as the vertex represents the highest or lowest point on the parabola.
Here's how to calculate the vertex step by step:
Here's how to calculate the vertex step by step:
- The x-coordinate of the vertex can be found using the formula: \[ x = -\frac{b}{2a} \] In our example, we have \[ a = -3 \] and \[ b = 0 \]
- Substitute these values into the formula: \[ x = -\frac{0}{2(-3)} = 0 \]
- Next, substitute this x-coordinate back into the original equation to find the y-coordinate. This means we calculate:
\[ f(0) = -3(0)^2 = 0 \] - Combine these results to get the coordinates of the vertex. For our example, the vertex of the parabola \[ f(x) = -3x^2 \]is at \((0, 0)\).