[x(x+3)]^(-1) = (1/3) [(x+3)-x] [x(x+3)]^(-1) = (1/3) [x^(-1) - (x+3)^(-1)]
同理
[(x+3)(x+6)]^(-1) = (1/3) [(x+3)^(-1) - (x+6)^(-1)]
[(x+6)(x+9]^(-1) = (1/3) [(x+6^(-1) - (x+9)^(-1)]
故方程可化简为
(1/3) [x^(-1) - (x+9)^(-1)] = 3(x+9)^(-1)
整理
x^(-1) = 10(x+9)^(-1)
即
x+9 = 10x
得
x=1
1/X - 1/(X+3) +1/(X+3) - 1/(X+6) + 1/(X+6) - 1/(X+9)= 1/X+9
1/X=2/X+9
X=9
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