1. Using letters Write five expressions which simplify to 2a – b + 3
[ A1.1 Core Starter]
Write five expressions which simplify to 2a – b + 3
Make them as complicated as you can!
Check each other’s expressions to make sure they are correct.
Write five equations which have x = 2 as their solution.
Check that each other’s equations have the correct solution x = 2.
Preamble
This activity, suitable for small groups, gives pupils the opportunity think a little deeper about simplifying and substituting into expressions, it gives practice in solving simple equations. Pupils, if possible, should be encouraged to move out of their comfort zone and devise complicated expressions. Obviously checking answers is an all important part of the activity and this could be done between small groups. If pupils are unsure you could start with:
simplify the example to 1 variable. E.g.: 2a + 3
Make the expression into an equation by using the equals sign. E.g.: 2a + 3 = 7
This would also provide an opportunity to explain the difference between an expression and an equation.
Possible content
Simplifying and substituting into algebraic expressions
Solution/Notes
Pupils’ own expressions and equations.
Possible examples for the 5 expressions:
Add /subtract a number to both sides: 2a – b + 5 = 2 (2 added to both sides)
Add/subtract a and/or b to both sides: 2a + 4b + 3 = 5b (5b added to both sides)
Multiply/divide by a number: 6a – 3b + 9 (multiplied by 3)
Including a variable that cancels: 2a – b + 2c + 3 = 2c
Possible examples for 5 equations :
Pupils could start with simple examples, but encourage them to not use a repeating strategy such as x + 1 = 3, 2x + 1 = 5, 3x + 1 = 7
Encourage pupils to use combinations to create multi-stage equations such as 4(3x -2) = 20 – 4
Pupils may quite happily use x on both sides in this context such as 5x + 3 = 7x - 1
Original Material © Cambridge University Press 2010
Original Material © Cambridge University Press 2010