Chapter 1: Problem 23
The Cartesian equation of a parabola is given. Determine its vertex and axis of symmetry. \(y=2 x-x^{2}\)
Short Answer
Expert verified
The vertex is at (1, 1) and the axis of symmetry is x = 1.
Step by step solution
01
Understand the Standard Equation Form
The standard form for a parabola is given by \[ y = ax^2 + bx + c \]In this form, the coefficient of the \(x^2\) term is \(a\), the coefficient of the \(x\) term is \(b\), and the constant term is \(c\). Here, we need to rearrange \[ y = 2x - x^2 \] to match the standard form.
02
Rewrite in Standard Form
To match the standard equation, rewrite the current equation in descending powers of \(x\):\[ y = -x^2 + 2x \]This means \(a = -1\), \(b = 2\), and \(c = 0\).
03
Identify the Vertex
The vertex of a parabola can be found using the formula \[ x = -\frac{b}{2a} \]Substitute the values of \(a = -1\) and \(b = 2\) into the formula:\[ x = -\frac{2}{2(-1)} = -\frac{2}{-2} = 1 \]So, the x-coordinate of the vertex is 1. To find the y-coordinate, substitute \(x = 1\) back into the original equation:\[ y = 2(1) - (1)^2 = 2 - 1 = 1 \]Therefore, the vertex is at \((1, 1)\).
04
Determine the Axis of Symmetry
The axis of symmetry of a parabola is the vertical line that passes through its vertex. Therefore, the equation for the axis of symmetry is \[ x = \text{(x-coordinate of vertex)} = 1 \]Thus, the axis of symmetry is \(x = 1\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Axis of Symmetry
The axis of symmetry is a vertical line that runs through the vertex of a parabola. It essentially splits the parabola into two mirror-image halves. This symmetry line is crucial because it helps to understand where the parabola is balanced. For a parabola in the form of \[ y = ax^2 + bx + c \]the axis of symmetry can be found using the formula:
The importance of the axis of symmetry cannot be understated, as it aids in graphing the parabola and understanding its properties. By solving the formula \(x = -\frac{b}{2a}\), you can easily determine where the parabola is symmetric, which in our example is at \(x = 1\).
This not only helps to define the structure of the parabola but also makes sure that any additional characteristics can be calculated with precision.
- \(x = -\frac{b}{2a}\)
The importance of the axis of symmetry cannot be understated, as it aids in graphing the parabola and understanding its properties. By solving the formula \(x = -\frac{b}{2a}\), you can easily determine where the parabola is symmetric, which in our example is at \(x = 1\).
This not only helps to define the structure of the parabola but also makes sure that any additional characteristics can be calculated with precision.
Standard Form of a Parabola
Understanding the standard form of a parabola is essential for analyzing its properties. The standard form is given by:
- \(y = ax^2 + bx + c\)
- \(a\): the leading coefficient affecting the parabola's width and direction.
- \(b\): the linear coefficient impacting the parabola's sideways motion.
- \(c\): the constant term representing the y-intercept.
Identifying Coefficients
Identifying coefficients in the quadratic equation is a straightforward but crucial step in understanding a parabola. These values dictate various characteristics of the graph. The quadractic standard form of a parabola, which is the most common form for calculations, is given by:
- \(y = ax^2 + bx + c\)
- \(a\): Determines the direction and steepness of the parabola.
- \(b\): Affects the horizontal location of the vertex and the parabola's symmetry.
- \(c\): The y-intercept of the parabola.
- \(a = -1\)
- \(b = 2\)
- \(c = 0\)
Vertex Calculation
The vertex of a parabola is the peak or the lowest point of the curve, depending on the direction of its opening. Calculating the vertex is a key task since it reveals important information about the parabola's position in the coordinate plane. The formula for finding the x-coordinate of the vertex from a quadratic equation in standard form is:
- \(x = -\frac{b}{2a}\)
- \(x = -\frac{2}{2(-1)} = 1\)
- \(y = 2(1) - (1)^2 = 1\)