how to solve 7x-9 9x+7

7x-9> 9x+7

7x-9x>9+7

-2x>16

x<-8

7x-9>9x+7
因為7x同9x係同項,即係都有個x,而9同7都係常數項
so..9x移過去,左邊變成7x-9x.....-9移過去,右邊變成7+9
即7x-9x > 7+9
-2x > 16
又因為個負號要移過右邊,所以大於符號要變成小於符號
即x < -8

7x-9> 9x+7
7x-9x>9+7
-2x>16
x<16/-2
x<-8

7x-9> 9x+7
-2x>16
x<-8


prove:
x = -7
7(-7)-9> 9(-7)+7
-58 < -56 wrong

x = -9
7(-9)-9> 9(-9)+7
-70 > -74 right

x = -8
7(-8)-9> 9(-8)+7
-65 = -65 wrong

7x-9> 9x+7
7x>9x+7+9
7x-9x>16
-2x>16
x<-8(當除-數個陣,,倒轉符號!!!!!!)

7x-9> 9x+7
7x-9x> 7+9
-2x> 16
x< 16/-2
x< -8

7x-9>9x+7
-2x>16
x<8

2007-07-31 17:57:09 補充：
打錯左 應該係x<-8