Algebra Learning Companion
1. What is Algebra?
Algebra is a branch of mathematics that uses letters (variables) to represent unknown numbers. Instead of working only with numbers like in arithmetic, algebra allows us to write general rules and solve problems systematically.
2. Understanding Equations
An equation is a mathematical statement showing that two expressions are equal. The sign “=” divides the equation into a left side and a right side.
Example:
$$x + 5 = 12$$
In this equation:
- The left side is: x + 5
- The right side is: 12
- x is the unknown variable we need to find
Key Principle:
An equation is like a balance scale. Whatever you do to one side, you must do to the other side to keep it balanced.
3. Solving Linear Equations: Step-by-Step
The Golden Rule:
To solve an equation, we isolate the variable on one side. This means:
- Move all terms with the variable to the left side
- Move all constant numbers to the right side
- Simplify and solve
Important Operations:
Rule 1: Addition and Subtraction
If a term is added on one side, subtract it from both sides:
$$x + 5 = 12 \implies x + 5 – 5 = 12 – 5 \implies x = 7$$
If a term is subtracted on one side, add it to both sides:
$$x – 3 = 8 \implies x – 3 + 3 = 8 + 3 \implies x = 11$$
Rule 2: Multiplication and Division
If the variable is multiplied by a number, divide both sides by that number:
$$3x = 15 \implies \frac{3x}{3} = \frac{15}{3} \implies x = 5$$
If the variable is divided by a number, multiply both sides by that number:
$$\frac{x}{2} = 6 \implies \frac{x}{2} \times 2 = 6 \times 2 \implies x = 12$$
4. Multi-Step Equations
Sometimes we need multiple steps to solve an equation. Follow these strategies:
Complete Example:
Solve: $2x + 5 = 13$
Step 1: Subtract 5 from both sides
$$2x + 5 – 5 = 13 – 5$$
$$2x = 8$$
Step 2: Divide both sides by 2
$$\frac{2x}{2} = \frac{8}{2}$$
$$x = 4$$
Step 3: Check
Substitute x = 4 back into the original equation:
$$2(4) + 5 = 8 + 5 = 13 \checkmark$$
5. Equations with Variables on Both Sides
When variables appear on both sides, collect them on one side:
Example:
Solve: $3x + 2 = x + 10$
Step 1: Move x to the left by subtracting x from both sides
$$3x – x + 2 = x – x + 10$$
$$2x + 2 = 10$$
Step 2: Move 2 to the right by subtracting 2
$$2x = 8$$
Step 3: Divide by 2
$$x = 4$$
6. Quick Tips and Tricks
- Balance is Key: Always do the same operation to both sides
- Opposite Operations: Use opposite operations to “undo” what’s done to the variable (add→subtract, multiply→divide)
- Always Check: Substitute your answer back into the original equation
- Order Matters: First handle addition/subtraction, then multiplication/division
- Combine Like Terms: Terms with the same variable can be added or subtracted
Easy Exercises
Solve for x in each equation:
Medium Exercises
Solve for x in each equation:
Hard Exercises
Solve for x in each equation: