Page 21 - 新思维数学活动用书8 样章

2 Expressions, formulae and equations

2.3 Expanding brackets

Exercise 2.3 Key words

brackets
Focus

You can use a box method to multiply numbers, like this: expand
3 × 14 = 3 × (10 + 4)

× 10 4 Tip
3 30 12 3 × (10 + 4) can be
3 × 14 = 30 + 12 = 42 written as
1 Copy and complete the boxes to work out the answers. 3(10 + 4).

a 4 × 18 b 3 × 21 You use the
× 10 8 × 20 1 table to expand

4 3 the bracket
3(10 + 4) to get
4 × 18 = + = 3 × 21 = + = 3× 10 + 3 × 4.
2 Copy and complete the boxes to show two different ways to multiply 6
by 58.

a 6 × 58 = 6 × (50 + 8) b 6 × 58 = 6 × (60 − 2) Tip
× 50 8 × 60 −2 Your answers to
6 6 a and b should
be the same.
6 × 58 = + = 6 × 58 = + =
3 Copy and complete the boxes to simplify these expressions. Some
have been started for you.
a 3(x + 5) b 2(x + 9)

× x 5 × x 9
3 3x 2

3(x + 5) = 3x + 2(x + 9) = +
c 5(y − 1) d 4(y − 8)

× y −1 × y −8

5 −5 4 4
5(y − 1) = − 5 4(y − 8) = −

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