Chapter 12: Problem 47
Graph each function using the vertex formula. Include the intercepts. \(g(x)=2 x^{2}-4 x+4\)
Short Answer
Expert verified
The vertex of the parabola is V(1, 2), the x-intercept is (1, 0) coinciding with the vertex, and the y-intercept is (0, 4). To graph the function \(g(x) = 2x^2 - 4x + 4\), plot these points and sketch an upward-opening parabola.
Step by step solution
01
Find the vertex
The vertex formula is given by \[x = \frac{-b}{2a}\], where a and b are the coefficients in the quadratic function \(g(x) = ax^2 + bx + c\). In this case, \(a = 2\) and \(b = -4\). Plugging these values into the formula to find the x-coordinate of the vertex, we get \[x = \frac{-(-4)}{2(2)} = \frac{4}{4} = 1\]. To find the y-coordinate of the vertex, plug the x-coordinate back into the function: \[g(1) = 2(1)^2 - 4(1) + 4 = 2 - 4 + 4 = 2\]. Therefore, the vertex of the parabola is V(1, 2).
02
Find the intercepts
To find the x-intercepts, we set the function equal to zero and solve for x: \[0 = 2x^2 - 4x + 4\].
However, it's difficult to factor this equation or solve for x directly. So, let's use the quadratic formula to find the x-intercepts: \[x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\]. With \(a = 2\), \(b = -4\), and \(c = 4\), we get:
\[x = \frac{-(-4) \pm \sqrt{(-4)^2 - 4(2)(4)}}{2(2)} = \frac{4 \pm \sqrt{0}}{4}\].
Since the discriminant is 0 (\(b^2 - 4ac = 0\)), there is only one x-intercept: \[x = \frac{4}{4} = 1\]. This means the x-intercept coincides with the vertex, and the point is (1,0).
To find the y-intercept, we set \(x = 0\) and solve for \(g(x)\): \[g(0) = 2(0)^2 - 4(0) + 4 = 4\]. This gives us the y-intercept at the point (0, 4).
03
Plot the points and sketch the parabola
Now we have the vertex V(1, 2), the x-intercept (1, 0), and the y-intercept (0, 4). Plot these points on a graph, and then sketch the parabola using these points, remembering that the graph opens upwards (since the coefficient \(a = 2 > 0\)). This will give you the graph of the function \(g(x) = 2x^2 - 4x + 4\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Function
A quadratic function is a type of polynomial function with the highest degree of 2. It is generally expressed in the form \(g(x) = ax^2 + bx + c\), where:
The key characteristic of a quadratic function is its curve shape, which is symmetrical and can open upwards or downwards.
- \(a\), \(b\), and \(c\) are constants
- \(a\) is not equal to zero (otherwise it wouldn't be a quadratic)
The key characteristic of a quadratic function is its curve shape, which is symmetrical and can open upwards or downwards.
- If \(a\) is positive, the parabola opens upwards.
- If \(a\) is negative, it opens downwards.
Parabola Graphing
Graphing a parabola is an essential skill when dealing with quadratic functions.
A parabola is a U-shaped curve that reflects the graph of a quadratic equation. The most critical point in a parabola is the vertex, which is its highest or lowest point depending on its orientation.
In the equation \(g(x) = 2x^2 - 4x + 4\):
A parabola is a U-shaped curve that reflects the graph of a quadratic equation. The most critical point in a parabola is the vertex, which is its highest or lowest point depending on its orientation.
In the equation \(g(x) = 2x^2 - 4x + 4\):
- The vertex was found at (1,2), where the curve reaches its minimum.
- The vertex can be found using the vertex formula \(x = \frac{-b}{2a}\)
Intercepts
Intercepts are points where the graph crosses the x-axis or y-axis.
- **X-intercepts** are points where \(g(x) = 0\). They represent where the graph meets the x-axis.
- **Y-intercept** is the point where \(x = 0\) and the graph meets the y-axis.
- We found the y-intercept at (0,4) by substituting \(x = 0\), yielding \(g(0) = 4\).
- The x-intercept coincided with the vertex at (1,0), because the discriminant (\(b^2 - 4ac\)) equaled zero. This means there was only one x-intercept.
Quadratic Formula
The quadratic formula is a powerful tool used to find the roots of a quadratic equation, specifically pointing out where the function touches or crosses the x-axis (x-intercepts).
It is expressed as: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] Here, the values \(a\), \(b\), and \(c\) are the coefficients from the quadratic function \(ax^2 + bx + c\). This solution mechanism is invaluable, especially when factoring is difficult or impossible. In our lesson:
It is expressed as: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] Here, the values \(a\), \(b\), and \(c\) are the coefficients from the quadratic function \(ax^2 + bx + c\). This solution mechanism is invaluable, especially when factoring is difficult or impossible. In our lesson:
- We used the quadratic formula and found that the discriminant \(b^2 - 4ac\) was zero. This indicated that the quadratic equation has exactly one solution.
- This single solution was corroborated by the fact that the vertex and x-intercept coincided.