Algebraic Foundations
TL;DR
Algebra is like a puzzle where you use letters (variables) to represent unknown numbers. You'll learn to move these variables around to solve for their values. Mastering this helps you understand and solve many real-world problems.
1. The Mental Model
Think of algebra as a balancing scale. Whatever you do to one side, you must do to the other to keep it balanced. Your goal is to isolate the unknown (the variable) on one side of the scale.
2. The Core Material
What are Variables?
Variables are symbols, usually letters like 'x' or 'y', that stand in for numbers we don't know yet. They're like placeholders.
Expressions vs. Equations
- An expression is a mathematical phrase that can contain numbers, variables, and operations (like addition or subtraction). It doesn't have an equals sign.
- Examples:
x + 5, 3y - 7, 2a^2
- An equation is a statement that two expressions are equal. It always has an equals sign.
- Examples:
x + 5 = 10, 3y - 7 = 2, 2a^2 = 18
Solving Basic Equations
The main goal in algebra is often to "solve" an equation, which means finding the value of the variable that makes the equation true. We do this by using inverse operations.
- Addition and Subtraction are inverse operations: To undo adding 5, you subtract 5. To undo subtracting 3, you add 3.
- Multiplication and Division are inverse operations: To undo multiplying by 4, you divide by 4. To undo dividing by 2, you multiply by 2.
Rule of Thumb: Whatever you do to one side of the equation, you must do to the other side to keep it balanced.
Here's how to solve a common type:
Example: Solve for x in x + 7 = 12
1. Our goal is to get x by itself.
2. x has 7 added to it. The inverse operation of adding 7 is subtracting 7.
3. Subtract 7 from both sides of the equation:
x + 7 - 7 = 12 - 7
4. Simplify:
x = 5
Example: Solve for y in 4y = 20
1. Our goal is to get y by itself.
2. y is multiplied by 4. The inverse operation of multiplying by 4 is dividing by 4.
3. Divide both sides of the equation by 4:
4y / 4 = 20 / 4
4. Simplify:
y = 5
Combining Like Terms
"Like terms" are terms that have the same variables raised to the same powers. You can add or subtract like terms. You can't combine x with x^2, or x with y.
Example: Simplify 3x + 5 + 2x - 1
1. Identify like terms: 3x and 2x are like terms; `