2.原式=(x+1)/(x-1)(x+1)+(x-1)/(x-1)(x+1)=2x/(x-1)(x+1)=2x/(x^2-1)3.原式=c^2/abc-a^2/abc=(c^2-a^2)/abc4.原式=a/(a+1)(a-1)+(3a+1)/(a+1)(a-1)-(2a+3)/(a+1)(a-1)=(a+3a+1-2a-3)/(a+1)(a-1)=2(a-1)/(a+1)(a-1)=...