/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 9 A quadratic function is given. (... [FREE SOLUTION] | 91Ó°ÊÓ

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A quadratic function is given. (a) Express the quadratic function in standard form. (b) Find its vertex and its \(x\) - and \(y\) -intercept(s). (c) Sketch its graph. $$f(x)=x^{2}-6 x$$

Short Answer

Expert verified
The function is \(f(x) = x^2 - 6x\), vertex: (3, -9), x-intercepts: (0, 0) and (6, 0), y-intercept: (0, 0).

Step by step solution

01

Express in Standard Form

A quadratic function is typically expressed in the form \(f(x) = ax^2 + bx + c\). The given function is \(f(x) = x^2 - 6x\). Comparing this with the standard form, we see that \(a = 1\), \(b = -6\), and \(c = 0\). Therefore, the function is already in standard form: \(f(x) = x^2 - 6x + 0\).
02

Find the Vertex

The vertex of a quadratic function \(f(x) = ax^2 + bx + c\) can be found using the formula \(x = -\frac{b}{2a}\). For \(f(x) = x^2 - 6x\), we have \(a = 1\) and \(b = -6\). Thus, \(x = -\frac{-6}{2 \times 1} = 3\). Substitute \(x = 3\) into the function: \(f(3) = 3^2 - 6 \times 3 = 9 - 18 = -9\). Therefore, the vertex is \((3, -9)\).
03

Find x-intercept(s)

The \(x\)-intercept(s) occur where \(f(x) = 0\). Solve \(x^2 - 6x = 0\) by factoring: \(x(x - 6) = 0\). So, \(x = 0\) or \(x = 6\). Hence, the \(x\)-intercepts are \((0, 0)\) and \((6, 0)\).
04

Find the y-intercept

The \(y\)-intercept occurs at \(x = 0\). Substitute \(x = 0\) into the function: \(f(0) = 0^2 - 6 \times 0 = 0\). Thus, the \(y\)-intercept is \((0, 0)\).
05

Sketch the Graph

Start by plotting the vertex \((3, -9)\) and the intercepts \((0, 0)\) and \((6, 0)\). The parabola opens upwards because the coefficient of \(x^2\) is positive. Draw a smooth curve through these points to represent the parabola. The graph is symmetrical about the line \(x = 3\), and extend it according to the general shape of a parabola.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Vertex of a Parabola
The vertex of a parabola is a crucial point that serves as the peak or the valley of its curve. For a quadratic function in the form of \( f(x) = ax^2 + bx + c \), the vertex can be found using the formula \( x = -\frac{b}{2a} \). This formula helps us locate the x-coordinate of the vertex.
Once we have the x-coordinate, substituting it back into the quadratic equation gives us the corresponding y-coordinate, thus providing the complete vertex as the point \((x, y)\).
The vertex represents the minimum point if the parabola opens upwards (when \( a > 0 \)) and the maximum point if it opens downwards (when \( a < 0 \)). This point also serves as a line of symmetry for the parabola, meaning that the parabola is mirrored on either side of this line.
x-intercepts
The x-intercepts of a quadratic function are the points where the graph of the function crosses the x-axis. At these points, the output of the function is zero, i.e., \( f(x) = 0 \).
To find the x-intercepts, we solve the quadratic equation by setting the function equal to zero and factoring, completing the square, or using the quadratic formula. In the given function \( x^2 - 6x = 0 \), factoring gives us \( x(x - 6) = 0 \). Solving this provides two solutions: \( x = 0 \) and \( x = 6 \).
This means the parabola will intersect the x-axis at the points \((0, 0)\) and \((6, 0)\). These intercepts are particularly useful for sketching the graph, as they provide clear reference points on the horizontal axis.
y-intercept
The y-intercept of a quadratic function is the point where the graph crosses the y-axis. At this point, the x-value is zero.
To find the y-intercept, we substitute \( x = 0 \) into the quadratic equation \( f(x) = ax^2 + bx + c \). For the function \( x^2 - 6x \), substituting \( x = 0 \) results in \( f(0) = 0^2 - 6 \times 0 = 0 \).
Therefore, the y-intercept of this quadratic is \((0, 0)\). The y-intercept is another vital point used to make a quick sketch of the graph, providing a starting point on the vertical axis.
Standard Form of a Quadratic Function
A quadratic function is often expressed in its standard form, which is \( f(x) = ax^2 + bx + c \), where \( a \), \( b \), and \( c \) are constants. This format is helpful because it allows for straightforward identification of the function's key characteristics.
The coefficient \( a \) indicates the direction the parabola opens. It opens upwards when \( a > 0 \) and downwards when \( a < 0 \). The \( b \) term affects the vertex's position along the x-axis, and \( c \) represents the y-intercept directly if the parabola is graphed.
In our given function \( f(x) = x^2 - 6x \), comparing with the standard form, we find that \( a = 1 \), \( b = -6 \), and \( c = 0 \). This clearly shows that the function is already in standard form, simplifying further analysis of its graph.

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