Expressions, equations, formulae & identities

1. Expressions, equations, formulae & identities Can you explain what these key words mean? Can you give an example for each one?

2. 2a + 3b + c is an expression is an equation is a formula is an identity

3. Expression An expression is made up of numbers and symbols, but expressions never have an equals symbol or inequality signs. Here’s some examples: 2a 3x + 2 5y2

4. 6a2 + 7 is an expression is an equation is a formula is an identity

5. 2a + 3 = 21 is an expression is an equation is a formula is an identity

6. Equation An equation is made of two expressions that are linked by an equals sign Equations can be solved– this means you can find out what number the letter symbol stands for. Here’s some examples: 2a = 6 3x + 2 = 29 5y2=45

7. 2a2 = 18 is an expression is an equation is a formula is an identity

8. 2a2 + 18 is an expression is an equation is a formula is an identity

9. 2l + 2w = P is an expression is an equation is a formula is an identity

10. Formula A formula is a short way of writing some sort of rule, for example A=πr2is the formula for the area of a circle. A formula is a type of equation, but the symbols in a formula have set meanings, for example in the formula 2l + 2w = P l stands for length, w stands for width and P stands for perimeter.

11. is an expression is an equation is a formula is an identity

12. is an expression is an equation is a formula is an identity

13. is an expression is an equation is a formula is an identity

14. 2(a + 3) = 2a + 6 is an expression is an equation is a formula is an identity

15. Identity An identity is equation which is always true – this means it works no matter what number the letter stands for. There is a special symbol for an identity, this is sometimes used in place of the equals symbol. 2(a + 3) ≡ 2a + 6

16. 2a + 3b = a + 2b + a + b is an expression is an equation is a formula is an identity

17. F = ma is an expression is an equation is a formula is an identity

18. 2a + 3b = c is an expression is an equation is a formula is an identity

19. 5(x - 4) ≡ 5x - 20 is an expression is an equation is a formula is an identity

20. 5(x - 4) is an expression is an equation is a formula is an identity

21. 20(5 - x) = 100 - 20x is an expression is an equation is a formula is an identity

22. 5(x - 4) = 20 is an expression is an equation is a formula is an identity

23. Check up: Can you explain what these key words mean? Can you give an example for each one? expression equation formula identity