Math 1 · Unit 2 · Lesson 1 · part 1 of 8
The Words We Use
The vocabulary for this lesson, in one place.
Words we use
| Word | Plain English | What you do |
|---|---|---|
| Function | A rule that takes one input and gives back exactly one output. Put the same number in, you always get the same number out, and never two different numbers. | Ask: if I feed in a number, do I get back exactly one number? Then it is a function. |
| Input | The number you feed in. In a spreadsheet, the cell the formula points to. In f(4), the 4. | It is the x in the formula. |
| Output | The number that comes out. In a spreadsheet, what the formula cell shows. In f(4) = 7, the 7. | It is the f(x), or the y. |
| f(x) | Read it f of x: a function of x. f(x) = x + 3 says the formula is x + 3 and x is what feeds in. The parentheses are not multiplication. | To find f(5), replace every x in the formula with 5. |
| y | Another name for the output, f(x). Graphing books write y = x + 3. Calculus books write f(x) = x + 3. Same thing. | Read y = x + 3 and f(x) = x + 3 as the same rule. |
| Coordinate plane | Two number lines crossed at zero. The x-axis runs left and right, the y-axis runs up and down. They cross at the origin, (0, 0). | Every point on it has an address: (x, y). |
| Ordered pair | A point's address, (x, y). x first, then y. (3, 2) and (2, 3) are different points. | Walk sideways x steps first, then up or down y steps. |
| Table of values | Some inputs and the output for each one. Written x and y, or x and f(x). Either way, every row is a point. | Fill it in, then plot each row as (x, y). |
| Linear equation | A rule like y = 2x - 1: x times a number, plus a number. The points it makes line up. Next lesson: why, and what to do with that. | Pick some x values, find each y, plot the points. |