Chapter 8: Problem 56
Find the maximum or minimum value of \(y\) for each function. $$y=6+5 x^{2}$$
Short Answer
Expert verified
The minimum value of \(y\) is 6.
Step by step solution
01
Identify the type of function
The given function is a quadratic function of the form \[y = ax^2 + bx + c\]. In this case, the function is \(y = 5x^2 + 6\). For quadratic functions, the maximum or minimum value of \(y\) occurs at the vertex.
02
Determine the direction of the parabola
Since the coefficient of \(x^2\) (which is 5) is positive, the parabola opens upwards. This means that the function has a minimum value.
03
Find the x-coordinate of the vertex
The x-coordinate of the vertex of a quadratic function \[y = ax^2 + bx + c\] is given by \[x = -\frac{b}{2a}\]. In this problem, \(a = 5\) and \(b = 0\). So the x-coordinate is: \[x = -\frac{0}{2 \times 5} = 0\].
04
Find the y-coordinate of the vertex
To find the y-coordinate of the vertex, substitute the x-coordinate of the vertex back into the function: \[y = 6 + 5(0)^2 = 6\].
05
Determine the minimum value
Since the vertex represents the minimum point of the parabola, the minimum value of \(y\) is \(y = 6\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
parabola
A parabolic curve, or simply a parabola, is the graph of a quadratic function. Parabolas can open upwards or downwards depending on the coefficient of the squared term (x²). Here’s what to keep in mind:
- If the coefficient (a) of x² is positive, the parabola opens upwards.
- If the coefficient (a) of x² is negative, the parabola opens downwards.
vertex
The vertex is a crucial point on a parabola. It represents the highest or lowest point on the curve, depending on the direction of the parabola. For the quadratic function \[y = ax^2 + bx + c\], the x-coordinate of the vertex can be found using the formula
\tag{x = -\frac{b}{2a}}.
Once you have the x-coordinate, substitute it back into the original function to find the y-coordinate. So, the vertex is at the point (x, y). This is particularly useful because:
\tag{x = -\frac{b}{2a}}.
Once you have the x-coordinate, substitute it back into the original function to find the y-coordinate. So, the vertex is at the point (x, y). This is particularly useful because:
- It helps to determine the maximum or minimum value of the function.
- It’s the point where the function changes direction.
minimum value
In a quadratic function where the parabola opens upward (a > 0), the vertex represents the minimum value of the function. Conversely, if the parabola opens downward (a < 0), the vertex represents the maximum value. Here’s a quick way to find both:
- After finding the x-coordinate of the vertex using \[x = -\frac{b}{2a}\], substitute it back into the function to get the y-coordinate.
quadratic formula
The quadratic formula is often used to find the roots of a quadratic equation \[ax^2 + bx + c = 0\]. Although it is not directly needed to find the vertex, it’s essential to understand it because:
\tag{x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}}.
Using this formula, you can find where the parabola intersects the x-axis. This is critical for both theoretical and practical applications.
- It can help solve quadratic equations for x.
- Understanding its derivation strengthens your grasp of quadratic functions.
\tag{x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}}.
Using this formula, you can find where the parabola intersects the x-axis. This is critical for both theoretical and practical applications.