Chapter 10: Problem 79
Sketch the graph of each equation. If the graph is a parabola, find its vertex. If the graph is a circle, find its center and radius. $$y=5 x^{2}-20 x+16$$
Short Answer
Expert verified
The graph is a parabola with vertex at (2, -4).
Step by step solution
01
Identify the Graph Type
The given equation is \( y = 5x^2 - 20x + 16 \), which is a quadratic equation in the form of \( y = ax^2 + bx + c \). This type of equation represents a parabola.
02
Find the Vertex Formula
The vertex of a parabola given by \( y = ax^2 + bx + c \) can be found using the formula for the x-coordinate of the vertex: \( x = -\frac{b}{2a} \).
03
Calculate the x-coordinate of the Vertex
For the equation \( y = 5x^2 - 20x + 16 \), we have \( a = 5 \) and \( b = -20 \). Substitute these values into the vertex formula: \( x = -\frac{-20}{2 \times 5} = 2 \).
04
Calculate the y-coordinate of the Vertex
Substitute \( x = 2 \) back into the original equation to find the y-coordinate: \( y = 5(2)^2 - 20(2) + 16 \). Simplify to get \( y = 20 - 40 + 16 = -4 \).
05
Write the Vertex Coordinates
Combine the x-coordinate and y-coordinate to state the vertex of the parabola. The vertex is \( (2, -4) \).
06
Sketch the Parabola
To sketch the parabola, plot the vertex \( (2, -4) \). The parabola opens upwards because the coefficient \( a = 5 \) is positive. Draw a symmetric curve around the vertex.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Vertex of a Parabola
In the world of parabolas, the vertex stands as the most crucial point. It's where the parabola changes direction.
To find the vertex of a parabola given by the quadratic equation \( y = ax^2 + bx + c \), you use a simple formula for the x-coordinate: \( x = -\frac{b}{2a} \). This formula is derived from the process of completing the square, a method used to turn a quadratic equation into its vertex form.
Here's how it works:
To find the vertex of a parabola given by the quadratic equation \( y = ax^2 + bx + c \), you use a simple formula for the x-coordinate: \( x = -\frac{b}{2a} \). This formula is derived from the process of completing the square, a method used to turn a quadratic equation into its vertex form.
Here's how it works:
- First, identify the coefficients \( a \) and \( b \) from the equation. For example, in \( y = 5x^2 - 20x + 16 \), \( a = 5 \) and \( b = -20 \).
- Substitute these values into the formula: \( x = -\frac{-20}{2 \times 5} = 2 \).
Quadratic Equation
Quadratic equations form the basis of parabolas and many real-world phenomena. They are equations of the second degree, meaning they have a variable squared, usually in the form \( y = ax^2 + bx + c \). Here, \( a \), \( b \), and \( c \) are constants, with \( a eq 0 \). This form is known as the standard form of a quadratic equation.
The characteristics of a quadratic equation include:
The characteristics of a quadratic equation include:
- The direction of the parabola, determined by the sign of \( a \). If \( a > 0 \), the parabola opens upwards (like a smile); if \( a < 0 \), it opens downwards (like a frown).
- The vertex, as discussed previously, which can be seen as the turning point of the parabola.
- The axis of symmetry, a vertical line that passes through the vertex, ensuring the parabola is symmetrical on either side.
Graph of a Quadratic Function
Graphing a quadratic function involves plotting its parabolic shape. To do this, you need some essential components determined from its quadratic equation:
The following steps are key in sketching the graph:
The following steps are key in sketching the graph:
- Identify the Vertex: Use the vertex formula to find this point, as it dictates the parabola's position and shape.
- Plot Additional Points: Choose x-values on either side of the vertex to establish symmetry and shape.
- Draw the Parabola: Use the vertex and the plotted points to draw a smooth, U-shaped curve. Ensure it opens in the direction indicated by the sign of \( a \).
- Locate the Y-intercept: This point is where the parabola crosses the y-axis, simply \( c \) from the equation when \( x = 0 \).