[(x-1)/(x+1)-(x+1)/(x+2)]*(x+2)²/(x+3)
=[(x²-1)-(x²+2x+1)](x+2)²/(x+1)(x+2)(x+3)
=-2(x+1)(x+2)²/(x+1)(x+2)(x+3)
=-2(x+2)/(x+3)