X除以（X-2） + （X-9）除以（X-7) = (X+1)除以（X-1） +（X-8)除以（X-6）
(x-2+2/x-2)+(x-7-2/x-7)=(x-1+2/x-1)+(x-6-2/x-6)
1+(2/x-2)+1-(2/x-7)=1+(2/x-1)+1-(2/x-6)
(1/x-2)-(1/x-7)=(1/x-1)-(1/x-6)
(1/x-2)+(1/x-6)=(1/x-7)+(1/x-1)
x-6+x-2/(x-2)(x-6)=x-1+x-7/(x-1)(x-7)
2x-8/(x-2)(x-6)=2x-8/(x-1)(x-7)
2x-8=0
x=4