把e^x和x^2+1看成是u和v,利用求导公式u'v-uv'/v^2
对于求导,一般形式如y=(ab)'=a'b+ab'
所以:y'=[(e^x)'(x²+1)-(e^x)(x²+1)']/(x²+1)²
=(e^x)(x²-2x+1)/(x²+1)²
=(e^x)(x-1)²/(x²+1)²
y=e^x/(x²+1)
y'=[(e^x)'(x²+1)-(e^x)(x²+1)']/(x²+1)²=(e^x)(x²-2x+1)/(x²+1)²=(e^x)(x-1)²/(x²+1)²
y'=((1-x^2)/(x^2+1)^2)·e^x/(x^2+1)