The idea in one sentence
Algebra is just arithmetic where some of the numbers are wearing a mask. The mask is usually a letter like x or y, and our job is to figure out who's under it.
1. Variables and expressions
A variable is a placeholder for a number we don't know yet. An expression is a combo of numbers, variables, and operations — no equals sign.
All three above are expressions. They represent a value, but they aren't saying anything equals anything yet.
2. Combining like terms
Terms are "like" if they use the same variables raised to the same powers. You can add or subtract their coefficients; the variable part stays the same.
Think of it like apples: 4 apples + 9 apples − 2 apples = 11 apples. Different fruit (different variables)? Leave it alone.
3. Worked example
Simplify: 5(2x − 3) + 4x − 1
- Distribute the 5 into the parentheses: 10x − 15.
- Bring down the rest: 10x − 15 + 4x − 1.
- Combine like terms — the x's and the constants: 14x − 16.
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