Page 20 - 新思维数学活动用书8 样章

2.2 Using expressions and formulae

Challenge

13 When x = −4, all of these expressions except one have the
same value.
Which is the odd one out?

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x − 7 (x +1 ) 2 − x −5 2x + 17 5 − x
2
x
14 Write any values of x that make each pair of expressions equal.
a 3x + 1 and 3x + 1 b 4 − x and x − 4
2
2x
c 5x + 5 and + 5 d 3(x + 2) and 2(x + 3)
2 5
15 a Use the formula D = wp + 4 to work out the value of D when w = 2.5
and p = 6.
b Rearrange the formula D = wp + 4 to make p the subject.
c Use your formula to work out the value of p when D = 100 and

w = 12.
16 The formula below is used to calculate the distance travelled
by an object. Tip

s ut + 1 at where: s = distance 1 at means
2
=
2
2
2
u = starting speed 1
a = acceleration 2 ××at 2
t = time
Work out the distance travelled by an object when
a u = 0, a = 6 and t = 5 b u = 30, a = −4 and t = 10

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