Introduction to Algebra
Year 7 📊 Algebra Understand variables, write and simplify algebraic expressions.
🔤 Letters for Numbers
Algebra uses letters (called variables) to represent unknown or changing numbers.
Example: If a bag of apples costs $p$ pence, then 4 bags cost $4p$ pence. We do not need to know $p$ exactly — we can still write expressions involving it.
$3n$ means $3 \times n$. We drop the multiplication sign in algebra.
📝 Writing and Simplifying Expressions
An expression is a collection of terms. Simplify by collecting like terms (same variable and power).
⚡ Like Terms
Only add or subtract terms with the same variable: $3x + 5x = 8x$, but $3x + 5y$ cannot be simplified.Example: Simplify $4a + 7 + 2a - 3$ → $(4a + 2a) + (7 - 3) = 6a + 4$
🔢 Substitution
Substitution means replacing a variable with a number to evaluate an expression.
Example: Find the value of $5x - 3$ when $x = 4$ → $5(4) - 3 = 20 - 3 = 17$
Example: If $a = 2$ and $b = -3$, find $a^2 + 2b$ → $4 + (-6) = -2$
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Interactive Demonstration — Introduction to Algebra
🔤 Algebra Starter Tool
Evaluate any expression by substituting a value for x.