Page 18 - 新思维数学活动用书9 样章

2.2 Constructing expressions

8 Write an expression for the area of each shape.
Write each expression in its simplest form.
a b
y
y
y

x
c d
x
4x
x 2

4x

9 The diagram shows a triangle.
The lengths of the sides of the triangle are written as expressions. g 2 g(8 – g)
a When g = 5, work out the lengths of the sides of the triangle.
b Use your answers to part a to work out the perimeter of 2g(3g – 11)

the triangle.
c Write an expression for the perimeter of the triangle.
Show that the expression can be simplified to 6g − 14g.
2
d Substitute g = 5 into the expression for the perimeter in part c.
Check your answers to parts b and d are the same.

10 For each rectangle, write an expression for
i the perimeter ii the area.
Write each answer in its simplest form.
Use the values given, and the same method as in Question 9, to check your expressions are

correct.
a a + 3 b b – 4
5 5

a = 3
b = 12

c c d 7d
c – 8
d 2
c = 10
d = 5

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