Unit 3
Algebraic expressions.
Letters that stand for numbers: like terms, expanding brackets and factorising, with every product drawn as a rectangle.
Before this unit
The unit, lesson by lesson
Lessons
4 lessons · 20 practice questions · about 2 hours
Letters and like terms
A letter that stands for a number, how to put a number into an expression, and why three x plus two x can be added, but three x plus two y cannot.
Expanding brackets
Why a number before brackets multiplies every term inside: a product is the area of a rectangle, and a rectangle whose side is split is cut into parts. And what a minus before brackets does.
Multiplying two brackets
A product of two sums is a rectangle with four parts: where the middle term comes from, why the square of a sum is more than the sum of the squares, and what happens when a side has a minus.
Factorising
Expanding brackets the other way round: when the areas are known, look for the sides. A common factor, a letter in common, sum and product, and the difference of two squares.