M3.8.4 For the adult
Brackets
Each of 3 children gets a tin with x beans and 4 more loose beans. How many beans is that in all?
What this chapter teaches
A number outside brackets multiplies every term inside them, so 3(x + 4) = 3x + 12. Factorising goes the other way: take out the highest common factor and check by expanding.
Three questions to ask
There is no one right wording. Listen for the idea.
- What is 3(x + 4) when x is 1? What is 3x + 4 when x is 1?
- Why must the 3 multiply the 4 as well as the x?
- How can you check that 4(2x + 3) is the same as 8x + 12?
After the chapter, the learner can
- Expand 3(x + 4) to get 3x + 12
- Factorise 6x + 9 as 3(2x + 3)
What they copy into their notebook
The number outside brackets multiplies every term inside. 3(x + 4) = 3x + 12. To factorise, take out the highest common factor. Check by expanding.