Question

若函数f(x)在负无穷到正无穷内满足f(x)的导数=f(x),且f(0)=1,则f(x)=e的x次方

Answer 1

由于f(x)=f′(x), 1=f′(x)/f(x) 两边不定积分 x+C(常数)=∫f′(x)/f(x)dx=∫df(x)/f(x)=∫dlnf(x)=lnf(x)
所以f(x)=e^(x+C),又因为f(0)=1,带入有C=0, 所以f(x)=e^x