Page 22 - 新思维数学活动用书9 样章

2.3 Expressions and indices

2.3 Expressions and indices

You can use the rules for indices with numbers for algebraic expressions.

Remember these rules:
b
i x × x = x a+b ii x ÷ x = x a−b iii x ( ) = x ab
a
b
a
b
a
Exercise 2.3

Focus

1 Match each rectangular card with the correct oval card. Tip

A x × x 4 B x × x 5 C x × x 2 D x × x 2 For expression D,
7
3
2
remember x = x .
1
i x 9 ii x 6 iii x 3 iv x 8

2 Match each rectangular card with the correct oval card.

A x ÷ x 2 B x ÷ x 5 C x ÷ x 4 D x ÷ x
4
8
9
10

i x 8 ii x 6 iii x 2 iv x 3

3 Two of these statements are true and two are false.
Write ‘True’ or ‘False’ for each statement.
If the statement is false, write the correct answer.

a y × y = y 6 b y × y = y 20
4
5
3
3
c y ÷ y = y 5 d y ÷ y = y 3 Tips
6
9
3
4 Copy and complete. When you add or
2
5
×
×
a ( ) = g 42 b ( ) = h 65
6
4
g
h
subtract variables
= g = h with the same
10
7
2
×
c ( ) = i 37 d ( ) = j 210 power, you do
×
3
j
i
not change the
= i = j
indices.
5 Copy and complete. The first one has been done for you. For part d of
a 3x + 5x = 8x 2 b 7x + 9x = x 3 Question 5,
2
3
3
2
remember
c 6y − 2y = y d 12y − y = y
6
6
4
4
y = 1y , so you
6
6
need to work
out 12 − 1.
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