**Middle School Number Sense Lesson 46: Functions (without Exponents)**

This concept works the same way as

**SubstDirect**, which we discussed for a high school lesson a couple of months ago. Functions without exponents appeared

**5 times**last year, usually at

**question # 46**.

**Number Dojo Level: 200**

A

**function**is a relation between a set of inputs and the related outputs--based on the rules and properties of the function. Each input of a function is related to exactly one output. A typical function looks like:

**f(x) = 3x - 5**

**f of x equals 3 x minus 5**." To find the output of a certain input x, simply substitute that input each time you see the x in the function.

A function's

**domain**is the set of possible inputs, and its

**range**is the set of its possible outputs.

**Example 1: If f(x) = 2x - 19, then f(6) = ___**

- Substitute 6 for x.
- 2(6) - 19 = 12 - 19 =
**-17**

Example 2: If f(x) = .25x + x, then f(8) = ___

Example 2: If f(x) = .25x + x, then f(8) = ___

- Substitute 8 for x.
- .25(8) + 8 = 2 + 8 =
**10**

**Example 3: If f(x) = 11/x, then f(1/9) = ___**

- Substitute 1/9 for x.
- 11/(1/9) = 11 x 9 =
**99**

**Example 4: If f(x) = 5/x + 2, then f(1/4) = ___**

- Substitute 1/4 for x.
- 5/(1/4) + 2 = 5 x 4 + 2 = 20 + 2 =
**22**

**Example 5: If f(x) = 11x, then f(37) = ___**

- Substitute 37 for x.
- 11(37) =
**407**

**Here's a free worksheet to help you practice Function:**

function.pdf |

**Up Next for Middle School: SetsSubsets**