Page 28 - 新思维数学学生用书9 样章

2.2 Constructing expressions

2 Luis thinks of a number, x.

Write an expression, in terms of x, for the number Luis gets when he:
a multiplies the number by 7
b subtracts the number from 20
c multiplies the number by 2, then adds 9
d divides the number by 6, then subtracts 4

e multiplies the number by itself
f divides 100 by the number
g subtracts 7 from the number, then multiplies the result by 5 Tip

h square roots the number Remember that
i cubes the number you write the
j cube roots the number cube root like
k multiplies the number by 3, squares the result, then adds 7 this 3
l multiplies the number by 2, cubes the result, then subtracts 100.

3 Write an expression for i the perimeter and ii the area of each rectangle.
Write each expression in its simplest form.
a y b y c 2y

x
3x 3x

d x e 2x f x 2
x
2x 2x

4 This is part of Mia’s homework.

Question
Write an expression for the perimeter and x + 5
area of this rectangle. 2x
Write each answer in its simplest form.

Answer
Perimeter = x + 5 + 2x + x + 5 + 2x
= 6x + 10

Area = 2x(x + 5)
= 2x + 10x
2

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