Chapter 9: Problem 27
Graph each of the functions. $$f(x)=-2 \sqrt{x}$$
Short Answer
Expert verified
The graph is a downward curve starting at the origin with points (0,0), (1,-2), (4,-4).
Step by step solution
01
Identify the Function Type
The given function is a square root function with a negative coefficient, making it a transformation of the basic square root function \( f(x) = \sqrt{x} \). The transformation includes a vertical scaling (multiplication by \(-2\)).
02
Determine Key Points
To graph the function, start by calculating key points. Choose a set of values for \( x \) such as 0, 1, and 4, and plug them into the function to find their corresponding \( y \)-values. For example, \( f(0) = -2\sqrt{0} = 0 \), \( f(1) = -2 \sqrt{1} = -2 \), and \( f(4) = -2 \sqrt{4} = -4 \).
03
Plot Key Points
Plot the calculated key points on the graph: \((0, 0)\), \((1, -2)\), and \((4, -4)\). These points help define the shape of the graph.
04
Sketch the Graph
Draw a smooth curve through the plotted points to trace out the shape of the function \( f(x) = -2\sqrt{x} \). The graph will start at the origin \((0, 0)\), pass through \((1, -2)\), and \((4, -4)\), continuing in that path, showing that as \(x\) increases, \(f(x)\) becomes more negative.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding the Square Root Function
The square root function is a fundamental concept in mathematics and is often represented as \( f(x) = \sqrt{x} \). This function takes any non-negative number \(x\) and returns its square root. For example, \( \sqrt{4} = 2 \) because 2 times 2 is 4. Graphically, the square root function starts at the origin \(0,0\) and moves upward and to the right, forming a distinctive curve known as a parabola's side. This curve gets closer and closer to being flat as \(x\) increases, which visually shows that the growth rate of the square root function diminishes.
- This function only applies to \(x \geq 0\), since the square root of a negative number isn't real—hence the graph is only in the first quadrant of the Cartesian plane.
- The key points to know by heart include \( (0,0) \), \( (1,1) \), and \( (4,2) \).
- Each point on the graph can be generated by plugging an \(x\) value into the function.
Exploring Vertical Scaling
Vertical scaling is a type of transformation that alters the height of a graph. When we apply vertical scaling to a function, we multiply its output values by a constant factor. For the given function \( f(x) = -2 \sqrt{x} \), the factor here is \ -2\.
- Vertical scaling by -2 implies that for every point on the original curve of \( f(x) = \sqrt{x} \), we need to stretch the curve en route to making it twice its initial distance from the \( x \)-axis, and then flip it over the \( x \)-axis due to the negative sign.
- This can radically change the shape and direction of a graph.
- Key examples start with \( f(1) = -2 \), where the point that was originally at \( (1, 1) \) now finds itself at \( (1, -2) \).
Diving into Function Transformations
Function transformations can reposition a graph in various ways, including translations, reflections, and scalings. In our case of the function \( f(x) = -2\sqrt{x} \), we see a combination of transformations.
- The first transformation we notice is the reflection over the x-axis. This happens because the coefficient \(-2\) is negative, flipping the graph upside down.
- The second transformation, as covered, is vertical scaling – the graph stretches downward by a factor of 2.
- Start with the basic graph of \( \sqrt{x} \).
- Reflect this over the x-axis to deal with the negative sign.
- Finally, apply vertical scaling to achieve the complete graph of \(-2\sqrt{x}\).