Page 16 - 新思维数学活动用书9 样章

2.2 Constructing expressions

2.2 Constructing expressions

In algebraic expressions, you use letters to represent unknown Key word

numbers. When you are asked to write an expression, think how you
would write it with numbers first. in terms of

Exercise 2.2 Tip

In Question 1a
Focus 4 + 2 can be

1 Add 2 to each of these numbers. Show your working. simplified to 6.

Parts a and c have been done for you.
a 4 4 + 2 = 6 b 10 ............................... Tip
c x x + 2 d z ...............................
2 Subtract 3 from each of these numbers. Show your working. In Question 1c
x + 2 cannot be
a 5 b 8 c y d z

3 Multiply each of these numbers by 5. Show your working. simplified so
leave it as x + 2.
a 2 b 4 c a d b
4 Divide each of these numbers by 5. Show your working. Tip

a 15 b 30 c a d b
5 Match each statement with the correct expression. In Question 3c
The first one has been done for you: A and iii. you can simplify
I think of a number n and... a × 5 to 5a.

A I add 15 i 15n
B I subtract 15 ii 3n + 5 Tip
C I multiply by 15 iii n + 15 In Question 4c
D I divide by 15 iv 5n − 3 you can simplify
a
E I subtract the number from 15 v n + 3 a ÷ 5 to .
5
5
F I multiply by 3 then add 5 vi n − 15
G I multiply by 5 then subtract 3 vii n
15
H I divide by 5 then add 3 viii 15 − n

15