Skip to main content
Logo image

Precalculus JumpStart

Exercises 6.11 Exercises

1. What is a Function?

Review Definition 6.2. Consider a typical telephone keypad.
There is the set of buttons
\begin{equation*} \{1,2,3,4,5,6,7,8,9,0,*,\#\} \end{equation*}
and the set of letters
\begin{equation*} \{A,B,C,D,E,\ldots,W,X,Y,Z\}. \end{equation*}
The association between the two determines a function. What are the inputs to this function? the buttons or the letters? What are the outputs? What is the domain of this function? What is the range?

2.

Let \(f(x) = \sqrt{2-x}\text{.}\)
  1. Evaluate \(f\) at \(x=7\text{,}\) if possible.
  2. Evaluate \(f\) at \(x=-7\text{,}\) if possible.
  3. What is the domain of \(f\text{?}\)
  4. When is \(f(x) = 0\text{?}\)

3. Evaluating Functions.

Suppose that \(f(x) = \sqrt{16+x^2}\) and \(g(x) = x^3+2x\text{.}\) Evaluate the expression completely. Show your work carefully as a sequence of equal expressions seperated with the equal sign.
\begin{equation*} \frac{f(-3)\cdot g(-1)}{2+\left[f(-3)\right]^2+g(-1^2)}. \end{equation*}
Answer.
\begin{equation*} \frac{f(-3)\cdot g(-1)}{2+\left[f(-3)\right]^2+g(-1^2)} = -5/8 \end{equation*}

4.

Given the defintions of \(f(x) = 1-2x^2\text{,}\) \(g(x) = \sqrt{2+x}\text{.}\) Find each expression and determine the domain. Then simplify the result, if possible.
  1. \(\displaystyle \displaystyle f-h\)
  2. \(\displaystyle \displaystyle fh\)
  3. \(\displaystyle \displaystyle f/h\)
  4. \(\displaystyle \displaystyle f \circ g \)
  5. \(\displaystyle \displaystyle g \circ f \)
  6. \(\displaystyle \displaystyle f \circ f\)
  7. \(\displaystyle \displaystyle h\circ k\)
  8. \(\displaystyle \displaystyle k\circ h\)
  9. \(\displaystyle \displaystyle g\circ k\)

5.

Let \(F(x) = 1/x\) and \(G(x) = \frac{1-x}{2x+3}\) Find each expression and determine the domain. Then simplify the result, if possible.
  1. \(\displaystyle (F\circ G)(x)\)
  2. \(\displaystyle (G\circ F)(x)\)
  3. \(\displaystyle (G\circ G)(x)\)
  4. \(\displaystyle (G\circF)(x)+2\)
  5. \(\displaystyle (G\circF)(x+2)\)

Inverse Functions.

6.

Suppose \(f\) is a one-to-one function satisfying \(f(0) = -1\text{,}\) \(f(1) = −1\text{,}\) and \(f(−1) = 0\text{.}\) Evaluate each expression below.
  1. \(\displaystyle f^{-1}(1)\)
  2. \(\displaystyle f^{-1}(0)\)
  3. \(\displaystyle -f(1)\)
  4. \(\displaystyle [f(0)]^{-1}\)
  5. \(\displaystyle (f^{-1}\circ f)(0)\)

7.

Given that each function is one-to-one, find its inverse function.
  1. \(\displaystyle f(x) = 4-3x\)
  2. \(\displaystyle g(x) = (4-3x)^3\)
  3. \(\displaystyle h(x) = \frac{1}{4-3x}\)
  4. \(\displaystyle h(x) = \frac{2x+1}{4-3x}\)
  5. \(\displaystyle k(x) = \frac{1}{\sqrt[5]{4-3x}}\)

8.

Explain why \(f(x) = \frac{1}{(2-x)^4}\) is not one-to-one.

9. Difference Quotients.

Find and simplify the difference quotient (6.2) for each function.
  1. \(\displaystyle f(x) = 4-2x\)
  2. \(\displaystyle f(x) = (4-2x)^2\)
  3. \(\displaystyle f(x) = \frac{1}{4-2x}\)