Year 9 Section 4

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…