设：x+2a=t；则x=t-2a,x+a=t-a,x+3a=t+a,x+4a=t+2a.所求为：1/(t-2a)+1/(t-a)+1/t+1/(t+a)+1/(t+2a)=2t/(t²-4a²)+2t/(t²-a²)+1/t=(5倍t的四次方-15a²t²+4倍a的四次方)/(t*(t²-4a...