Maths問題 20point

8.
4 X –­ 7 = X + X 5 4 5 4 4 X –­ 7 x 20 = X + X x 205 4 5 4 16x – 35 = 4x + 5x 16x – 35 – 9x = 9x - 9x 7x – 35 = 0 7x – 35 + 35 = 0 + 35 7x = 35 7x除7 = 35除7
x = 5

9.
4(x+2) = 7 + 5x 5 13 4(x+2) X 5 = 7 + 5x X55 13 4(x+2) = 35 + 25x 13 4 X x X 13 + 4 X 2 X13 = 35 X 13 + 25x X13 13 52x + 104 – 104 = 455 + 25x – 104 52x – 25x = 351 + 25x – 25x 27x除27 = 351除27 x = 13
10.
x + 35 – x + 7 = x + 21 6 9 4 x + 35 X 36 – x + 7 X 36 = x + 21 X 36 6 9 4 6(x + 35) – 4(x + 7) = 9(x + 21) 6 X x + 6 X 35 – 4 X x – 4 X 28 = 9 X x + 21 X 9 6x + 210 – 4x – 28 = 9x + 189 2x + 182 – 2x = 9x – 2x +189 182 – 189 = 7x -7除7= 7x除7 x = -1


2011-04-20 21:10:21 補充：
SOR!!!

我有D斜咗!

2011-04-20 21:10:22 補充：
SOR!!!

我有D斜咗!

你好～～～

有一條是不是重複了？？我做一次好了～～

8) (4 / 5)x - (7 / 4) = x / 5 + x / 4

4x / 5 - 7 / 4 = 4x / 20 + 5x / 20

(4x * 4) / 20 - (7 * 5) / 20 = 9x / 20

(16x - 35) / 20 = 9x / 20

16x - 35 = 9x

7x = 35

x = 5

9) 4(x + 2) / 5 = 7 + 5x / 13

4(x + 2) / 5 * 5 = 5 * (7 + 5x / 13)

4x + 8 = 35 + 25x / 13

4x + 8 = (455 + 25x) / 13

(4x + 8) * 13 = (455 + 25x) / 13 * 13

52x + 104 = 455 + 25x

52x - 25x = 455 - 104

27x = 351

x = 351 / 27

x = 13

10) (x + 35) / 6 - (x + 7) / 9 = (x + 21) / 4

[6 * (x + 35)] / 36 - [4 * (x + 7)] / 36 = 9(x + 21) / 36

[6(x + 35) - 4(x + 7)] / 36 = 9(x + 21) / 36

6x + 210 - 4x - 28 = 9x + 189

6x - 4x - 9x = 189 + 28 - 210

-7x = 7

x = -1

希望以上解答可以幫到你～～～～～