Page 50 - 新思维数学学生用书7 样章

2.4 Expanding brackets

9 The diagram shows a rectangle.

The width of the rectangle is 8 cm. 8 cm
The length of the rectangle is 3y + 4 cm. 3y + 4 cm
Write an expression, in its simplest form, for the:
a area of the rectangle
b perimeter of the rectangle

10 In the triangle ABC, the angle at A is (4k − 7m) °. B
The angle at B is two times the size of the angle at A.
Write an expression, in its simplest form, for the size of the
4k – 7m
angle at B.
C A
11 This is how Rachel expands and simplifies the expression
5(2x + 4) − 12.

5(2x + 4) – 12 = 5 × 2x + 5 × 4 – 12
= 10x + 20 – 12
= 10x + 8

Expand and simplify:
a 4(x + 7) − 1 b 7(x + 3) + 5x c 12 + 3(2x − 3)

Summary checklist

I can multiply out a bracket.

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