Single Transformations of Functions

Introduction

Vertical shift:

f(x)=x^{2}

(red) and

g(x)=x^{2}+4

(blue)

Horizontal shift:

f(x)=sin(x)

(red) and

g(x)=sin(x+{\frac {\pi }{2}})

(blue)

Vertical reflection:

f(x)={\sqrt {x}}

(red) and

g(x)=-{\sqrt {x}}

(blue)

Horizontal reflection:

f(x)=e^{x}

(red) and

g(x)=e^{-x}

(blue)

Translations

One kind of transformation involves shifting the entire graph of a function up, down, right, or left. The simplest shift is a vertical shift, moving the graph up or down, because this transformation involves adding a positive or negative constant to the function. In other words, we add the same constant to the output value of the function regardless of the input. For a function $g(x)=f(x)+k$ , the function $f(x)$ is shifted vertically k units. For example, $g(x)=x^{2}+4$ is the function $f(x)=x^{2}$ shifted up by 4 units. $g(x)=sin(x)-7.7$ is the function $f(x)=sin(x)$ shifted down by 7.7 units.

Given a function f, a new function $g(x)=f(x-h)$ , where h is a constant, is a horizontal shift of the function f. If h is positive, the graph will shift h units to the right. If h is negative, the graph will shift h units to the left. For example, $g(x)=(x-3)^{2}$ is the graph of $f(x)=x^{2}$ shifted 3 units to the right. $g(x)=sin(x+{\frac {\pi }{2}})$ is the function $f(x)=sin(x)$ shifted ${\frac {\pi }{2}}$ units to the left.

Reflections

Given a function $f(x)$ , a new function $g(x)=-f(x)$ is a vertical reflection of the function $f(x)$ , sometimes called a reflection about (or over, or through) the x-axis. For example, $g(x)=-{\sqrt {x}}$ is a vertical reflection of the function $f(x)={\sqrt {x}}$ .

Given a function $f(x)$ , a new function $g(x)=f(-x)$ is a horizontal reflection of the function $f(x)$ , sometimes called a reflection about the y-axis. For example, $g(x)=e^{-x}$ is a horizontal reflection of the function $f(x)=e^{x}$ .

Even and Odd Functions

A function f is even if for all values of x, $f(x)=f(-x)$ ; that is, a function $f(x)$ is even if its horizontal reflection $f(-x)$ is identical to itself. For example, $f(x)=x^{2}$ is an even function since $f(-x)=(-x)^{2}=(-1)^{2}(x)^{2}=x^{2}=f(x)$ .

A function f is odd if for all values of x, $f(x)=-f(-x)$ ; that is, a function $f(x)$ is odd if a horizontal reflection and vertical reflection of the function results in the same function. For example, $f(x)=x^{3}$ is an odd function since $-f(-x)=-(-x)^{3}=(-1)(-1)^{3}(x)^{3}=x^{3}=f(x)$ .

If a function satisfies neither of these conditions, then it is neither even nor odd. For example, $f(x)=x^{2}+x$ is neither even nor odd because $f(-x)=(-x)^{2}+(-x)=x^{2}-x$ , which is not equal to $f(x)$ , and $-f(-x)=-(-x)^{2}-(-x)=-x^{2}+x$ , which is also not equal to $f(x)$ .

Compressions and Stretches

Given a function $f(x)$ , a new function $g(x)=af(x)$ , where $a$ is a constant, is a vertical stretch or vertical compression of the function $f(x)$ .

If $a>1$ , then the graph will be stretched.
If $0<a<1$ , then the graph will be compressed.
If a < 0, then there will be a vertical stretch or compression of a factor of $|a|$ , along with a vertical reflection.

Given a function $f(x)$ , a new function $g(x)=f(bx)$ , where $b$ is a constant, is a horizontal stretch or horizontal compression of the function $f(x)$ .

If $b>1$ , then the graph will be horizontally compressed by a factor of ${\frac {1}{b}}$ .
If $0<b<1$ , then the graph will be horizontally stretched by a factor of ${\frac {1}{b}}$ .
If b < 0, then there will be a horizontal stretch or compression of a factor of $|<math>{\frac {1}{b}}$ | </math>, along with a vertical reflection.