# Year 9 Section 4

- Created by: OCTOBI
- Created on: 02-05-23 11:37

**How to solve inequalities:**

Rearrange the inequality so the numbers are all on one side

e.g. 2x+ 3 < 21 becomes 2x < 18

Rearrange the inequality by dividing the coefficient:

e.g. 2x < 18 becomes x < 9

Any value less than 9 satisfies this inequality.

**How to increase and decrease by a percentage:**

To increase by 12%, multiply by 1.12

To decrease by 12%, multiply by 0.88

This works as it is a proportion of the starting number.

**Repeated Percentage Change:**

To increase a number by 12% multiple times (in this example i use 4 times), multiply by 1.12^4.

To decrease a number by 12% four times, multiply by 0.88^4.

**Compund Interest: **

initial amount x multiplier ^time

e.g.

500 x 1.03^2 = 530.88

250 x 1.05^4 = 305.22

**Combining Transformations:**

Translations need a vector

Reflections need a mirror line

Rotations need a…

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