Algebraic expressions
Variables, constants, terms, coefficients, like terms. The grammar of algebra.
An expression is a maths sentence with no equals sign: 3x + 5, or 2a + 7b - a. Like terms can be combined: 2a - a = a. Coefficients (the number in front of a letter) add when terms match.
Worked examples
3x + 4x = 7x. Like terms.
2a + 5b + 3a − b = 5a + 4b.
4(x + 3) means ‘4 lots of x+3’ = 4x + 12.
Frequently asked questions
xy or x×y?
Convention: write next to each other. xy = x × y. x×y is reserved for arithmetic where confusion is possible.
Why is 3x + 5 not the same as 8x?
3x and 5 are unlike terms (one has x, one doesn't). They cannot combine.