解4x+9y=2y+3x+4=5x+7y+5

☆ヾ(◕‿◕)ノ
　我知道你係學校唔開心～
　　唔好放棄～
　　　搵ｄ好朋友多ｄ傾下～
　　　　跟住畀心機讀書！

4x + 9y = 2y + 3x + 4 = 5x + 7y + 5

拆兩條式做，否則無野做到．．．

{4x + 9y = 2y + 3x + 4
{4x + 9y = 5x + 7y + 5

{x + 7y = 4 ...[1]
{-x + 2y = 5 ...[2]

[1]+[2] 得 9y = 9

y = 1

[1]: x + 7 = 4

x = -3

所以：
{ x = -3
{ y = 1