Page 20 - 新思维数学学生用书9 样章

2 Expressions and

formulae

Getting started

1 Sara thinks of a number, x. She divides the number by 3, then adds 7.
Write an expression for the number Sara gets.
2 Copy and complete

5
a 3 × 3 = 3 b 5 12 = 5 c ( ) = 7
4
2
2
7
3 Expand 5 9
a x(x + 2) b 3y(4y – 7w)
4 Factorise
a 4x + 12 b 4x + 14x
2
5 Work out

1
a 3 + 2 b 2 − 1 3
4 3 2 10
6 a Use the formula F = ma to work out F when m = 10 and a = 2.5.

b Rearrange the formula F = ma to make a the subject.
c Use your formula in part b to work out a when F = 72 and m = 12.