Chapter 2: Problem 43
In Problems \(43-46,\) describe in words how the graph of the first function is obtained from the graph of the second function using rigid and nonrigid transformations. Carefully graph the first function. $$ y=-1+2 \sqrt{-x+2} ; y=\sqrt{x} $$
Short Answer
Expert verified
Reflect \( y=\sqrt{x} \) over the y-axis, shift right 2 units, stretch vertically by 2, and shift downward by 1.
Step by step solution
01
Understanding the Functions
We need to compare the given functions: the first function is \( y = -1 + 2 \sqrt{-x+2} \) and the second function is \( y = \sqrt{x} \). We will describe how to transform \( y = \sqrt{x} \) into \( y = -1 + 2 \sqrt{-x+2} \) using transformations.
02
Transformation Step 1: Horizontal Reflection and Shift
The expression \( \sqrt{-x+2} \) involves a horizontal reflection and horizontal shift. The negative sign in \(-x\) reflects the function \( y = \sqrt{x} \) across the y-axis. Additionally, \(-x + 2\) can be rewritten as \(-(x - 2)\), indicating a shift 2 units to the right.
03
Transformation Step 2: Vertical Stretch
The coefficient 2 in \( 2\sqrt{-x+2} \) means a vertical stretch by a factor of 2. This affects the steepness of the original graph, effectively doubling each y-value from the graph of \( \sqrt{-x+2} \).
04
Transformation Step 3: Vertical Shift
The term \(-1\) is a vertical shift that moves the entire graph downward by 1 unit. This transformation affects every point on the graph by decreasing each y-value by 1.
05
Graphing the Transformed Function
Begin by drawing the basic shape of \( y = \sqrt{x} \). Reflect it across the y-axis to represent \( \sqrt{-x} \), then shift it 2 units to the right to achieve \( \sqrt{-x+2} \). Apply a vertical stretch by multiplying all y-values by 2 and, finally, shift the entire graph down by 1 unit to complete \( y = -1 + 2\sqrt{-x+2} \) graphically.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Horizontal Reflection
A horizontal reflection is an exciting transformation. It flips a graph over the y-axis. If you have a function like \( y = \sqrt{x} \), applying a horizontal reflection involves changing the sign inside the square root, resulting in \( y = \sqrt{-x} \). Now, the graph that used to stretch from the origin toward the right will stretch from the origin toward the left instead. Reflecting a graph is like looking at its mirror image along the y-axis.
Transformations build upon each other, and here, this reflection will be followed by a shift.
- Points on the right side of the original graph move to the left in the reflection.
- The shapes remain the same, but reversed.
Transformations build upon each other, and here, this reflection will be followed by a shift.
Vertical Stretch
Vertical stretch alters the height of the graph, making it taller or shorter. It's like zooming in or out vertically.The transformed function, \( y = 2\sqrt{-x+2} \), involves a vertical stretch.This stretch reflects in a change of scale for the y-values.When multiplying a function by a number greater than one, like 2 in this case, every y-value of \( \sqrt{-x+2} \) becomes twice as large.
- The graph appears steeper.
- Each point's vertical distance from the x-axis is doubled.
Vertical Shift
The vertical shift is a simple movement of the graph up or down.In the function \( y = -1 + 2\sqrt{-x+2} \), this is represented by the \(-1\) term. It tells us to move the entire graph of \( 2\sqrt{-x+2} \) downward by one unit.This affects every point on the graph equally.So, each y-value decreases by one:
- It does not change the shape of the graph.
- Only its vertical position on the coordinate plane shifts.
Graphing Functions
Graphing a function involves sketching it on a set of axes.For our example, we start with the base function \( y = \sqrt{x} \).Transforming this into \( y = -1 + 2\sqrt{-x+2} \) involves applying each transformation in sequence.Follow these steps:1. Reflect the graph horizontally over the y-axis to obtain \( y = \sqrt{-x} \).2. Shift it to the right by 2 units to achieve \( \sqrt{-x+2} \).3. Apply a vertical stretch, making the graph steeper, providing \( 2\sqrt{-x+2} \).4. Finally, shift it down by 1 unit to get the final form \( y = -1 + 2\sqrt{-x+2} \).Each change alters the graph’s standing:
- Reflections change the graph's orientation.
- Stretches adjust its steepness.
- Shifts move it to the required position.