Page 33 - 新思维数学活动用书7 样章

2 Expressions, formulae and equations

c 2(y − 4) d 6(k − 3)
× y −4 × k −3

2 6

2(y − 4) = − 6 (k − 3) = −

Practice
5 Expand the brackets.

a 3(a + 2) b 5(b + 3) c 3(c + 2) d 5(d − 1)
e 4(e − 9) f 3( f − 8) g 4(2 + f ) h 8(7 + z)
i 9(3 + y) j 4(4 − x) k 7(1 − w) l 7(2 − v)

6 Multiply out the brackets.
a 5(2p + 1) b 7(3q + 2) c 9(2r + 3)
d 11(3s − 4a + 7) e 2(2t − 5) f 4(5u − 1)
g 6(1 + 2v) h 8(6 + 4w − 3g) i 10(6 + 7x)
j 5(3 − 5x) k 5(4 − 3x) l 5(5k − 8x − 6h)

7 This is part of Paul’s homework. Paul has made a mistake in every solution.

Question
Multiply out the brackets.
a 5(a + 3) b 3(4b – 5) c 4(3 – c)
Solution

a 5(a + 3) = 5a + 3
b 3(4b – 5) = 12b – 8
c 4(3 – c) = 12 – 4c = 8c

Explain the mistakes Paul has made. Tip

8 Which one of these expressions is the odd one out? The ‘odd one
Explain your answer. out’ means the
2(9x + 12) 2(10x + 8) 6(4 + 3x) 3(8 + 6x) 1(18x + 24)
expression that is

different from all
of the others.

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