Page 43 - 新思维数学学生用书7 样章

2 Expressions, formulae and equations

Worked example 2.3

Simplify each expression.
a 2x + 3x b 7y − 2y c 4p + 3q + 2p − q d 5t + 7 − 3t + 3

Answer
a 2x + 3x = 5x 2x and 3x are like terms, so add them to get 5x.

b 7y − 2y = 5y 7y and 2y are like terms, so subtract to get 5y.
c 4p + 3q + 2p – q = 6p + 2q 4p + 2p = 6p and 3q − q = 2q, but 6p and 2q
are not like terms so you cannot simplify any
further.
d 5t + 7 − 3t + 3 = 2t + 10 5t − 3t = 2t and 7 + 3 = 10, but 2t and 10 are not
like terms so you cannot simplify any further.

Exercise 2.3

1 Erik has yellow, green and blue bricks.
The length of a yellow brick is a. a b c
The length of a green brick is b.
The length of a blue brick is c.

Work out the total length of these arrangements of bricks.
Give your answer in its simplest form.
a b
? ?
c d
? ?
e f
? ?
2 Match each expression, a to f, to its correctly simplified expression,
i to vi. Tip
The first one has been done for you: a and v. Remember that
a x + x i 7x x is the same as

b 5x + 4x ii x 1x.
c x + 6x iii 4x
d 5x − 2x iv 9x

e 2x − x v 2x
f 8x − 4x vi 3x

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