中二數學(~急~)
回答 (6)
2007-10-05 5:38 am
✔ 最佳答案
x = 7+ y __ (1)sub (1) into x - 9 = 2 (y - 9)
7 + y - 9 = 2 (y - 9)
2 + y = 2y - 18
y = 20
x = 7 +20 = 27
2007-10-04 21:39:26 補充：
x = 7+ y __ (1)sub (1) into x - 9 = 2 (y - 9)7 + y - 9 = 2 (y - 9)- 2 + y = 2y - 18y = 16x = 7 + 16 = 23
2007-10-05 5:45 am
先將 {x-y=7 變成 x=7+y
之後代入第2條式...> x-9=2(y-9) 寫做 7+y-9=2(y-9)
先乘右邊的數...> 7+y-9=2y-18
再放x及y放好...> 7-9+18=2y-y
之後就可以計到...> y=?
代y入x=7+y ...> x=7+?
就可以計到...自己計la...我唔知我會唔會寫錯
之後代入第2條式...> x-9=2(y-9) 寫做 7+y-9=2(y-9)
先乘右邊的數...> 7+y-9=2y-18
再放x及y放好...> 7-9+18=2y-y
之後就可以計到...> y=?
代y入x=7+y ...> x=7+?
就可以計到...自己計la...我唔知我會唔會寫錯
參考: me
2007-10-05 5:41 am
{x-y=7-----------(1)
{x-9=2(y-9)------------(2)
from (1) x=7+y ----------------(3)
sub (3) into (2)
(7+y)-9=2(y-9)
7+y -9 =2y -18
7-9+18 =2y- y
16 = y ---------(4)
sub (4) into (1)
x-16 =7
x =23
最完整答案
{x-9=2(y-9)------------(2)
from (1) x=7+y ----------------(3)
sub (3) into (2)
(7+y)-9=2(y-9)
7+y -9 =2y -18
7-9+18 =2y- y
16 = y ---------(4)
sub (4) into (1)
x-16 =7
x =23
最完整答案
參考: 阿sir +我
2007-10-05 5:39 am
x-y=7----- *
x-9=2(y-9) ----- @
from *
x-y=7
x= 7+y ----- #
form @
x-9=2(y-9)
x - 9 = 2y -18
x- 2y +9 =0 ----$
Sub # into $
(7+y)-2y+9=0
7+9-y = 0
2-y = 0
y = 2
sub y = 2 into *
x -y =7
x - 2 =7
x = 9
x-9=2(y-9) ----- @
from *
x-y=7
x= 7+y ----- #
form @
x-9=2(y-9)
x - 9 = 2y -18
x- 2y +9 =0 ----$
Sub # into $
(7+y)-2y+9=0
7+9-y = 0
2-y = 0
y = 2
sub y = 2 into *
x -y =7
x - 2 =7
x = 9
2007-10-05 5:39 am
{x-y=7--------------1
{x-9=2(y-9)----------2
由 1 :x=y+7 代入2
y+7-9=2y-18
y=16
x=23
{x-9=2(y-9)----------2
由 1 :x=y+7 代入2
y+7-9=2y-18
y=16
x=23
2007-10-05 5:37 am
x-y = 7 ..............1
x-9 = 2(y-9).........2
from 1,
y=x-7
put y = x-7 in 2
x-9 = 2(x-7-9)
x-9 = 2x-32
x = 23
y = x-7=23-7=16
x-9 = 2(y-9).........2
from 1,
y=x-7
put y = x-7 in 2
x-9 = 2(x-7-9)
x-9 = 2x-32
x = 23
y = x-7=23-7=16
收錄日期: 2021-04-13 19:26:19
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20071004000051KK04191