原式＝(x+1)(x+2)/(x²+4x+4)*（3x+6)/(2x²-8)÷1/(x²-4)＝ (x+1)(x+2)/(x+2)²*3(x+2)/[2(x²-4)]×(x²-4)＝(x+1)/(x+2)*3(x+2)/2 ＝3(x+1)/2.