Factorising
Factorising
- Factorising is the opposite of expanding brackets
- You need to look for the largest factors you can take out of every term in the expression
Factorising x^2 + bx + c
- You need to write the expression with two brackets
- x^2 + 7x + 10
- You need to find two numbers which add up to 7 and multiply to make 10
- 5+2=7
- 5x2=10
- When factorising x^2 + bx + x use this table to help find the two numbers
| b | c | Factors |
|---|---|---|
| Positive | Positive | Both numbers positive |
| Positive | Negative | Bigger number positive and smaller number negative |
| Negative | Negative | Bigger number negative and smaller number positive |
| Negative | Positive | Both numbers negative |
Factorising ax^2 + bx + x
- One of the brackets must contain a ax term
- Try pairs of numbers which have a product of c
- Check each pair by multiplying out the brackets
Difference of two squares
- You can factorise expression that are written as something^2 - something else^2