Page 42 - 新思维数学学生用书7 样章

2.3 Collecting like terms

2.3 Collecting like terms

In this section you will … Key words

• collect like terms. collecting like

terms
Here are two different bricks. like terms
The length of the red brick is x cm. xcm ycm simplify

The length of the blue brick is y cm.
When you join together three red bricks,
the total length is 3x cm. When you join xcm + xcm + xcm = 3xcm
together two blue bricks, the total length
is 2y cm. When you join together three
ycm + ycm = 2ycm
red bricks and two blue bricks the total
length is 3x cm + 2y cm.
You can add, subtract or combine
xcm + xcm + xcm ycm + ycm = 3xcm + 2y cm
like terms.
You cannot combine terms that contain different letters.
You can simplify an expression by collecting like terms.
This means that you rewrite the expression in as short a way as possible.
This table shows examples of good practice when

you write simplified expressions.

✓ ✗
a 1a, 1 × a, a 1
2a a + a, 2 × a, a2
ab a × b, ba, b × a ✓ is the best way to write simplified expressions.
✗ is not the best way to write simplified expressions.
a a ÷ b
b
a 2 a × a

a 3 a × a × a

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