Page 47 - 新思维数学学生用书9 样章

2 Expressions and formulae

c Simplify these fractions. Use your favourite method.

i 10x + 30 ii 12x + 24 iii 16x − 48 iv 6 − 18x
5 6 4 2

While answering the questions in this exercise, you have used skills you
have learned before.
Make a list of the skills you have used while simplifying these algebraic

fractions (for example, one skill you have used is factorising expressions).
If you are not sure of the other skills, look back through the questions in
the exercise.

Summary checklist

I can simplify algebraic fractions.

2.6 Deriving and using formulae

In this section you will … Key words

• write and use formulae changing the
• change the subject of a formula. subject

subject of a
A formula is a mathematical rule that shows the relationship between formula
two or more variables. For example, a formula that is often used in

physics is: v = u + at
In this formula, v is the subject of the formula. It is written on its own, Tip
on one side of the equation. You usually write
Depending on the information you are given and the variable you want the subject of the

to find, you might need to rearrange the formula. This is called changing formula (in this
the subject of the formula. For example, if you know example, v) on
the values of v, a and t in the formula v = u + at and you v = u + at the left-hand side
want to work out the value of u, you would rearrange the u + at = v of the equation.

equation as shown. u = v − at
This makes u the subject of the formula.

46