=[(x+1)/2(x-1)-6/(x+1)(x-1)-(x+3)/2(x+1)]×4(x+1)(x-1)/3=(x+1)/2(x-1)×4(x+1)(x-1)/3-6/(x+1)(x-1)×4(x+1)(x-1)/3-(x+3)/2(x+1) ×4(x+1)(x-1)/3=2(x+1)²/3-8-2(x+3)(x-1)/3=(2x²+4x+2-2x²-4x+6)/3-8=8/3-8=-16/3
