Algebra

What you'll learn

Using letters to stand for numbers, and the rules for writing, simplifying and evaluating expressions.

• A **variable** is a letter such as \(x\) that stands for a number we do not know yet.
• A **term** is a number, a variable, or a product of them: \(5\), \(x\), \(3x\), \(2xy\).
• **Like terms** share the same variable part, so they combine: \(3x + 5x = 8x\); but \(3x + 5y\) cannot.
• To **evaluate**, substitute the value: if \(x = 4\), then \(3x + 2 = 3(4) + 2 = 14\).
• Multiplication is written without a sign: \(3 \times x = 3x\) and \(x \times x = x^2\).
• **Expand** a bracket by multiplying every term inside: \(3(x + 2) = 3x + 6\).