L1 · Expression or equation?

Learning goal

“I can explain the difference between an expression and an equation, and translate words into each one correctly.”

Expression — a mathematical phrase built from numbers, variables and operations, with NO equals sign (e.g. 3x + 5). It names a value but does not claim anything.

Equation — a mathematical statement with an equals sign, claiming the left side and the right side have the same value (e.g. 3x + 5 = 20).

Variable — a letter standing for a number that can change or is unknown (review from G7U05).

Side — one part of an equation: everything left of the equals sign is the left side; everything right of it is the right side.

Worked example

Two cards: 3x + 5 and 3x + 5 = 20. Step 1: Look for the equals sign. The first card has none. It is a phrase - it names a quantity ("3 times a number, plus 5") but claims nothing. It is an expression. Step 2: The second card has an equals sign. It makes a claim: "3x + 5 has the same value as 20." A claim that two sides are equal is an equation. Step 3: The test never fails: equals sign present -> equation; absent -> expression. The variable is not the test - both cards have one. Say it plainly: an expression is a phrase; an equation is a sentence. A sentence can be true or false - and in this unit we will find the variable values that make equations true.

Check yourself — explain it

What makes 3x + 5 = 20 an equation, while 3x + 5 is only an expression?

Paired problem — example still visible

Classify 7 - y. -> Expression (no equals sign; it names a value but claims nothing)

Faded completion — last step is yours

"'A number plus 9' written in symbols is ___, and it is an ___" -> n + 9; expression

Ready to practise?

10 scored questions with a 3-rung hint ladder. Mastery needs 8/10 plus both gate questions.

Start practice →Take the unit quiz