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## Algebra I (2018 edition)

### Unit 1: Lesson 5

Writing algebraic expressions introduction

# Writing expressions with variables

To write simple algebraic expressions from mathematical statements, you can follow this procedure: 1. Identify the key terms in the written statement (e.g. "sum," "product," "quantity"). 2. Break the statement down into its component parts. 3. Translate each part into algebraic form, using the appropriate symbols and operations. 4. Simplify the expression if needed. Created by Sal Khan.

## Video transcript

What I want to do in this video is write the algebraic expressions that represent the same thing that these statements are saying. So this first statement, they say the sum of negative 7 and the quantity 8 times x. So the sum-- so we're going to have an addition here-- of negative 7 and the quantity 8 times x. So the quantity 8 times x, well, that's just 8x. So I can just write 8x over there. So it is negative 7 plus 8x. Or you could view this as the sum of negative 7 and the quantity 8 times x. Let's do the next one. Take the quantity negative 3 times x and then add 1. So the quantity negative 3 times x, we can write that as negative 3x. And then we need to add 1 to that. So that's going to be plus 1. Now this one. Negative 6 plus-- so we can write negative 6 plus something-- the product of negative 1 and x. So the product of negative 1 and x, that's just going to be negative 1x, which is the same thing as negative x. So we can write this as negative 6 plus negative x. Or we can just write this-- this is the exact same thing as negative 6 minus x. And we are done.