方程式,5識做

7-1/2[x-1/5(6-x)]=3x+22

7-1/2[x-6/5+x/5]=3x+22

7-1/2[6x/5-6/5]=3x+22

7-3x/5+3/5=3x+22

7+3/5-22=3x+3x/5

35+3-110=15x+3x

-72=18x

-4=x

x=-4

2006-10-20 11:25:46 補充：
第六步驟是兩邊都乘5

7-1/2[x-1/5(6-x)]=3x+22
{14 - [x-1/5(6-x)]}/2 = 3x + 22
{14 - [x-1/5(6-x)]} = 2 (3x + 22)
14 - x + 1/5(6-x) = 6x + 44
1/5(6-x) = 6x + 44 - 14 + x
1/5(6-x) = 7x + 30
6 - x = 5 (7x + 30)
6 - x = 35x + 150
-x - 35x = 150 - 6
-36x = 144
x = 144 / (-36)
x = -4

7 - (1/2) [x - (1/5)(6-x)] = 3x + 22

為了避免分數運算錯誤，建議先兩邊倍大 2

14 - [x - (1/5)(6-x)] = 6x + 44

14 - x + (1/5)(6-x) = 6x + 44

再兩邊倍大 5

70 - 5x + (6-x) = 30x + 220

70 - 5x + 6 - x = 30x + 220

76 - 6x = 30x + 220

-144 = 36x

x = -144 /36

x = -4

7-(0.5)*[x-0.2*(6-x)] = 3x +22
-3x-(0.5)*[x-0.2*(6-x)] = 15 (putting the constant to one side)
-3x-0.5x+0.1(6-x) = 15 (remove the first bracket)
-3.5x-0.1x+0.6 = 15 (remove the second bracket)
-3.6x = 14.4
thus, x = - 4