Page 21 - 新思维数学学生用书9 样章

2 Expressions and formulae

You might not be surprised that computer

programmers, scientists, engineers and
statisticians all use algebra in their jobs.
But you might be surprised at some other jobs
that also need algebra.

Cooks and chefs prepare food for other
people. They work in all sorts of places, from
cafés and restaurants to international business
headquarters. They need to plan menus and

adapt recipes for the number of people they
are feeding. They must work out quantities
of ingredients, their cost and the price their
customers will pay for the food. They use

algebra when they deal with ingredients
and prices.
Farm and ranch managers deal with the day-
to-day activities of a ranch or farm. They use

algebra when they manage the farm accounts
and write yearly business plans. If they grow
crops, they need to plan how much fertiliser
to apply and when to put it on the crops. They

might use quite complicated algebra, as they need to consider lots of different things such as soil
type, crop to be grown, type of fertiliser, cost of fertiliser, etc.
Whatever job you do, you never know when algebra will be there to help you!

2.1 Substituting into expressions

In this section you will … Key word

• use the correct order of operations in algebraic counter-example
expressions.

Tip
When you substitute numbers into expressions, remember the correct
order of operations: Examples of
• Work out brackets and indices before divisions and multiplications. indices are 4 , 7 ,
2
3
• Always work out additions and subtractions last. (−2) and (−3) .
3
2

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