Expressions · Year 7
In Year 7 you learn: writing expressions and collecting like terms.
An algebraic expression uses letters to stand for numbers, like 3a + 2b. Simplifying it — collecting like terms and tidying products — makes it shorter and easier to work with, in the same way that 3 apples + 2 apples is 5 apples.
Key facts
- Collect like terms by adding their coefficients; each term keeps the sign in front of it: 5a − 2b − a = 4a − 2b.
- A letter on its own has a coefficient of 1: x means 1x.
Worked examples
Example 1
Simplify 7a + 3b − 2a + b.
Answer: 5a + 4b
Example 2
The sides of a triangle are 2x + 5, 3x − 1 and x + 4 cm. Write an expression for the perimeter, then find it when x = 6.
Answer: 6x + 8; 44 cm
Example 3
Simplify (5p + 2q) − (3p − 4q).
Answer: 2p + 6q