How_To_Be_Good_At_Math

Equations

An equation is a mathematical statement that contains an equals

sign. We can write equations using numbers, or with letters or other

symbols to represent numbers. This type of maths is called algebra.

The three laws of arithmetic

An equation must always follow the

three laws of arithmetic. We looked at

how these rules work with real numbers

on pages 154-55. We can also write the

same laws using algebra if we replace

the numbers with letters.

2 + 8 8 + 2

The commutative law

This law tells us that numbers can be added or

multiplied in any order and the answer will always

be the same. We can see how the commutative law

works with this addition calculation, and then write

the law using algebra.

Switching the numbers

produces the same result

Balancing equations

An equation must always

balance – whatever is to the left

of the equals sign has the same

value as whatever is to the right

of the equals sign. We can see

how this works when we look

at this addition equation.

Both sides of this

equation balance –

they are equal

The rules of arithmetic

help to make sure that

an equation balances.

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302 ALGEBRA •^ EQUATIONS

14

=

• 6

a + b b + a

WRITING WITH NUMBERS

WRITING WITH ALGEBRA

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