Chapter 6: Problem 75
Graph each equation by making a table of values. \(y=\frac{1}{2} x^{2}+2 x-6\)
Short Answer
Expert verified
Plot the points from table: (-3,-7.5), (-2,-8), (-1,-7.5), (0,-6), (1,-3.5), (2,0), (3,4.5), then draw a curve through them.
Step by step solution
01
Set up the equation
Write down the quadratic equation we need to work with: \[ y = \frac{1}{2}x^2 + 2x - 6 \]
02
Choose values for x
Select a range of x-values to calculate corresponding y-values. A good range to start with might be -3 to 3. This allows us to see the behavior of the quadratic equation across positive, negative, and zero x-values.
03
Calculate y-values
Substitute each chosen x-value into the equation and solve for y. For each x, compute:1. For \( x = -3 \), \[ y = \frac{1}{2}(-3)^2 + 2(-3) - 6 \] \[ y = \frac{1}{2}(9) - 6 - 6 \] \[ y = 4.5 - 6 - 6 = -7.5 \]2. For \( x = -2 \), \[ y = \frac{1}{2}(-2)^2 + 2(-2) - 6 \] \[ y = \frac{1}{2}(4) - 4 - 6 \] \[ y = 2 - 4 - 6 = -8 \]3. For \( x = -1 \), \[ y = \frac{1}{2}(-1)^2 + 2(-1) - 6 \] \[ y = \frac{1}{2}(1) - 2 - 6 \] \[ y = 0.5 - 2 - 6 = -7.5 \]4. For \( x = 0 \), \[ y = \frac{1}{2}(0)^2 + 2(0) - 6 \] \[ y = 0 - 6 = -6 \]5. For \( x = 1 \), \[ y = \frac{1}{2}(1)^2 + 2(1) - 6 \] \[ y = \frac{1}{2}(1) + 2 - 6 \] \[ y = 0.5 + 2 - 6 = -3.5 \]6. For \( x = 2 \), \[ y = \frac{1}{2}(2)^2 + 2(2) - 6 \] \[ y = 2 + 4 - 6 = 0 \]7. For \( x = 3 \), \[ y = \frac{1}{2}(3)^2 + 2(3) - 6 \] \[ y = 4.5 + 6 - 6 \] \[ y = 4.5 \]
04
Plot the points
Take the calculated pairs of (x, y) values and plot them on a graph. The points to plot are:
- (-3, -7.5)
- (-2, -8)
- (-1, -7.5)
- (0, -6)
- (1, -3.5)
- (2, 0)
- (3, 4.5)
05
Draw the graph
Once the points from Step 4 are plotted, connect them with a smooth curve to reveal the parabolic shape of the quadratic function. Ensure the curve reflects the function's symmetry and opens upwards.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Equation
A quadratic equation is a second-degree polynomial that can be written in the general form:\[ y = ax^2 + bx + c \]. Here, \(a\), \(b\), and \(c\) are constants, with \(a eq 0\). The equation given in the exercise is \(y = \frac{1}{2}x^2 + 2x - 6\). This specific equation has a coefficient \(a = \frac{1}{2}\), a linear term coefficient \(b = 2\), and a constant \(c = -6\). The term \(x^2\) indicates that the equation is quadratic in nature, meaning the graph of the equation forms a parabola. Quadratic equations have a wide range of applications, such as calculating projectile paths and optimizing areas.
Table of Values
Creating a table of values is essential for graphing a quadratic equation like \(y = \frac{1}{2}x^2 + 2x - 6\). This involves selecting a series of x-values, computing the corresponding y-values, and writing these pairs in a tabular form.
This table helps in accurately plotting points on the graph and visualizing the parabola. Tables of values are a handy tool for visual understanding, particularly in algebra.
- Start by picking x-values. It's often helpful to choose values both negative and positive, as well as zero, to fully capture the shape of the graph.
- Then, substitute each x-value into the quadratic equation to find the y-value.
- Finally, organize these pairs of values (x, y) in a table.
This table helps in accurately plotting points on the graph and visualizing the parabola. Tables of values are a handy tool for visual understanding, particularly in algebra.
Parabola
A parabola is the graph of a quadratic equation drawn on a coordinate plane. It has a unique U-shape and can either open upwards or downwards. The direction in which the parabola opens depends on the sign of the coefficient \(a\) from the quadratic equation.
For \(y = \frac{1}{2}x^2 + 2x - 6\), since \(a = \frac{1}{2}\), the parabola opens upwards. Parabolas also have several key features:
For \(y = \frac{1}{2}x^2 + 2x - 6\), since \(a = \frac{1}{2}\), the parabola opens upwards. Parabolas also have several key features:
- The vertex, the highest or lowest point on the graph, depending on whether it opens up or down.
- An axis of symmetry, a vertical line passing through the vertex that divides the parabola into two mirror-image halves.
- The y-intercept, where the parabola crosses the y-axis, which can be found by setting \(x\) to zero in the equation.
X-values
In the context of graphing a quadratic equation, x-values are selected input values used to calculate corresponding y-values.
Choosing the right range of x-values is important for capturing the overall shape of the parabola. Generally, a range that includes both negative and positive numbers—as well as zero—is recommended. For this exercise:
Choosing the right range of x-values is important for capturing the overall shape of the parabola. Generally, a range that includes both negative and positive numbers—as well as zero—is recommended. For this exercise:
- We used x-values from -3 to 3.
- This range was chosen to include the vertex and sufficient points on either side of it, ensuring the graph's symmetry is visible.
Y-values
Y-values are the outputs obtained from substituting the chosen x-values into the quadratic equation. These values describe how high or low the graph will go based on each x.
For our quadratic equation \(y = \frac{1}{2}x^2 + 2x - 6\), each x-value results in a specific y-value:
These y-values are then paired with their respective x-values to plot points on the graph, helping us trace the parabola.
For our quadratic equation \(y = \frac{1}{2}x^2 + 2x - 6\), each x-value results in a specific y-value:
- The y-value is calculated by performing operations outlined in the equation, such as squaring x, multiplying by coefficients, and adding/subtracting terms.
- For example, an x-value of -3 results in a y-value of -7.5. Performing this computation step-by-step ensures accuracy.
These y-values are then paired with their respective x-values to plot points on the graph, helping us trace the parabola.