In this worksheet, you must find the formula which matches the results in the given table.

You can easily do this by testing each formula.

**Example**

Find the formula which matches the results in this table.

a | b |
---|---|

2 | 5 |

3 | 7 |

4 | 9 |

10 | 21 |

Which formula will match the results?

1. ** b = 2a**

2. **b = 3a - 1**

3. **b = 2a + 1**

**Answer**

We test out each formula in turn.

**b= 2a** doesn't work for any of the rows

**b= 3a - 1** works for when a = 2 and b = 5 , but not for the other rows

**b = 2a + 1** works for all the rows, as you have to double the **a** number and add 1 to get the** b **number.

The answer is** b = 2a + 1**