Chapter 13: Problem 39
Write each equation of a parabola in standard form and graph it. Give the coordinates of the vertex. $$ y=2 x^{2}-4 x+5 $$
Short Answer
Expert verified
The vertex is at \((1, 3)\) and the standard form of the parabola is \( y = 2(x-1)^2 + 3 \).
Step by step solution
01
Identify the form of the equation
The given equation is already in the form of a quadratic equation which is \( y = ax^2 + bx + c \). For the given equation, \( a = 2 \), \( b = -4 \), and \( c = 5 \).
02
Find the vertex using the vertex formula
The vertex of a parabola in the form \( y = ax^2 + bx + c \) can be found using the formula \( x = -\frac{b}{2a} \). Substitute the values of \( b \) and \( a \) from the equation: \( x = -\frac{-4}{2(2)} = \frac{4}{4} = 1 \).
03
Calculate the y-coordinate of the vertex
Substitute the \( x \) value from Step 2 back into the original equation to find the \( y \)-coordinate. \[ y = 2(1)^2 - 4(1) + 5 = 2 - 4 + 5 = 3 \] So, the vertex is at \((1, 3)\).
04
Write the equation in vertex form
The vertex form of a parabola is \( y = a(x-h)^2 + k \), where \((h, k)\) is the vertex. Given \( a = 2 \) and the vertex \((1, 3)\), the vertex form is: \[ y = 2(x-1)^2 + 3 \]
05
Graph the parabola
To graph the parabola, plot the vertex at \((1, 3)\). Since \( a = 2 \), the parabola opens upwards and is relatively narrow. You can choose additional points on either side of the vertex, calculate their corresponding \( y \)-values, and plot them to complete the graph.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Parabola Vertex
The vertex of a parabola is a crucial point that signifies its peak or trough. In mathematical terms, a parabola is described by a quadratic equation of the form \( y = ax^2 + bx + c \). The vertex of a parabola can be easily located using the vertex formula, \( x = -\frac{b}{2a} \). This formula allows us to find the x-coordinate of the vertex, which we then use to determine the y-coordinate by plugging it back into the original equation.
- For our example, with \( a = 2 \), \( b = -4 \), substituting into the formula gives \( x = 1 \).
- Next, substituting \( x = 1 \) back into the equation \( y = 2x^2 - 4x + 5 \), we find that \( y = 3 \).
Standard Form
The standard form of a quadratic equation is a necessary tool for understanding parabolas and their properties. It is expressed as \( y = ax^2 + bx + c \). This makes it straightforward to identify the equation's parameters and features, such as the parabola's width and orientation.
- Parameter \( a \): Determines the direction the parabola opens (upward if \( a > 0 \), downward if \( a < 0 \)) and its width (more narrow for larger \|a\| values).
- Parameters \( b \) and \( c \): Affect the parabola in terms of its horizontal shift and vertical shift on the y-axis.
Vertex Form
Converting a quadratic equation into vertex form can simplify the process of identifying the vertex and understanding the parabola's behavior. The vertex form is expressed as \( y = a(x-h)^2 + k \), where \((h, k)\) is the vertex of the parabola. This form provides immediate access to the vertex' position just by looking at the formula.
- \( a \) remains the same as in the standard form, indicating the direction and shape of the parabola.
- \( h \) and \( k \) are the x and y-coordinates of the vertex, making the equation easily interpretable.