(1)、
1 - 1/(x²+7x+6) =1 - 1/(x²+5x+6),
所以
x²+7x+6=x²+5x+6,
解得x=0
(2)、
x/(1-x) +x/(1+x) =2x/(1-x²),
故
x/(1-x) +x/(1+x) + 2x/(1+x²)+ 4x/(1+x^4)
=2x/(1-x²) + 2x/(1+x²)+ 4x/(1+x^4)
=4x/(1-x^4) + 4x/(1+x^4)
=8x/(1-x^8)=0,
解得x=0
(3)、
(x+2)/(x+1) - (x+4)/(x+3)=(x+6)/(x+5) - (x+8)/(x+7)
所以
1/(x+1) -1/(x+3)= 1/(x+5) -1/(x+7),
故
x² +4x +3= x² +12x +35
即8x= -32,
解得x= -4