解方程{(a+2)x+(a+1)y=a{ (b+2)x+(b+1)y=bTHANK YOU VERY MUCH!

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解方程{(a+2)x+(a+1)y=a{ (b+2)x+(b+1)y=bTHANK YOU VERY MUCH!
解方程
{(a+2)x+(a+1)y=a
{ (b+2)x+(b+1)y=b
THANK YOU VERY MUCH!

解方程{(a+2)x+(a+1)y=a{ (b+2)x+(b+1)y=bTHANK YOU VERY MUCH!
上下相减:得x+y=1
上下相加:得(A+B+4)X+(A+B+2)Y=A+B
设A+B=C,则原方程为(C+4)X+(C+2)Y=C
两边同时相加2Y得:(C+4)X+(C+4)Y=C+2Y
(C+4)(X+Y)=C+2Y
把x+y=1代进去得
所以C+4=C+2Y
所以2Y=4
所以Y=2
所以X=-1