原式=[(3-x)/(x²-9)]÷﹛x+2-[5/(x-2)]﹜
=﹛[-(x-3)]/[(x+3)(x-3)]﹜÷﹛[(x+2)(x-2)-5]/(x-2)﹜
=[-1/(x+3)]÷[(x²-4-5)/(x-2)]
=[-1/(x+3)]÷[(x²-9)/(x-2)]
=[-1/(x+3)]×(x-2)/[(x+3)(x-3)]
=-(x-2)/[(x+3)²(x-3)],
=(x-2)/[(x+3)²(3-x)],化簡后與你給出的結(jié)果一樣
當x=2√2時
原式=(2√2-2)/[(2√2+3)²(3-2√2)]
=(2√2-2)/[(3+2√2)(3+2√2)(3-2√2)]
=(2√2-2)/[(3+2√2)(9-8)]
=(2√2-2)/(3+2√2)
=[(2√2-2)(3-2√2)]/[(3+2√2)(3-2√2)]
=[(2√2)×3-2√2×2√2-2×3+2×2√2]/(9-8)
=6√2-8-6+4√2
=(10√2)-14