Chapter 2: Problem 3
One of the variations on completing the square gives you the form \((c x+a)^{2}+b\). Does \(c\) represent a vertical stretch/shrink or a horizontal stretch/shrink of the function \(x^{2} ?\)
Short Answer
Expert verified
\(c\) represents a horizontal stretch/shrink of the function \(x^2\).
Step by step solution
01
Understand the Form
In the given expression \((cx+a)^2+b\), the goal is to understand the role of \(c\). The expression is derived from completing the square and is a transformed version of \(x^2\).
02
Compare to Standard Form
Recall the standard function \(x^2\). Transformations are indicated by different modifications outside and inside the parentheses: \(c(x+a/c)^2+b\). Here, \(a\) shifts horizontally, \(b\) shifts vertically, and \(c\) affects the stretching or shrinking.
03
Determine Role of c
The factor \(c\) inside the parentheses affects the \(x\)-term directly. To determine how, consider that multiplying by \(c\) affects its stretching or shrinking horizontally. Specifically, \(c > 1\) compresses horizontally, \(0 < c < 1\) stretches horizontally.
04
Conclusion on Stretch or Shrink
Since \(c\) is inside the function, it alters the horizontal scale: a factor affecting \(x\) on its own transforms the width of \(x^2\). Thus, \(c\) results in a horizontal stretch or shrink.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Horizontal Stretch
A horizontal stretch in a function transformation occurs when the function's shape is widened along the x-axis. It is achieved by multiplying the x-term by a factor between 0 and 1. Think of it as pulling the graph outward, making it appear broader.
When we apply a horizontal stretch to a quadratic function like \(y = x^2\), it means the parabola will become wider. This transformation does not affect the vertex's position on the graph but changes how rapidly the function increases or decreases. For instance:
When we apply a horizontal stretch to a quadratic function like \(y = x^2\), it means the parabola will become wider. This transformation does not affect the vertex's position on the graph but changes how rapidly the function increases or decreases. For instance:
- If you have \((0.5x)^2\), this represents a horizontal stretch by a factor of 0.5.
- The graph appears twice as wide compared to the graph of \(x^2\) alone.
Horizontal Shrink
A horizontal shrink is the opposite of a horizontal stretch. It occurs when the function is compressed along the x-axis. You achieve this by multiplying the x-term by a factor greater than 1. In visual terms, it's like squeezing the graph inward.
For a quadratic function such as \(y = x^2\), a horizontal shrink causes the parabola to become narrower, focusing the graph more towards the y-axis. The vertex stays put, but the parabola's arms will steepen. For example:
For a quadratic function such as \(y = x^2\), a horizontal shrink causes the parabola to become narrower, focusing the graph more towards the y-axis. The vertex stays put, but the parabola's arms will steepen. For example:
- In \((2x)^2\), the function undergoes a horizontal shrink by a factor of 2.
- The graph appears half as wide as \(x^2\).
Function Transformation
Function transformation is a broad term that describes how changes in the equation of a function affect its graph. There are several transformations, including translations, reflections, stretches, and shrinks.
Transformations modify the graph's shape, position, and orientation. For instance:
Transformations modify the graph's shape, position, and orientation. For instance:
- Horizontal translations move the graph left or right without altering its shape. This is typically seen in expressions like \(x+a\).
- Vertical translations shift the graph up or down, seen in terms like \(x^2 + b\).
- Reflections flip the graph over a line, such as the x-axis, usually involving a negative sign.
- Stretches and shrinks alter the graph's width and height, affecting both x-axis and y-axis dimensions depending on where in the equation these occur.
Quadratic Function
A quadratic function is a polynomial function with a degree of 2, generally expressed as \(y = ax^2 + bx + c\). Its graph is a parabola, which can open either upwards or downwards, depending on the sign of the coefficient \(a\).
Key features of quadratic functions include:
Key features of quadratic functions include:
- The vertex, which is the highest or lowest point depending on the orientation of the parabola.
- The axis of symmetry, a vertical line through the vertex that divides the parabola into symmetric halves.
- The y-intercept, which is the point where the graph crosses the y-axis, determined by the constant \(c\).