1.记y=f(x)=ax^2+bx+c,y=g(x)=e^x,那么
f'(x)=2ax+b,f''(x)=2a,g'(x)=g''(x)=e^x
根据题意,f(0)=g(0),f'(0)=g'(0),
f''(0)=g''(0)
有c=1,b=1,a=1/2,k=f'(0)=1
切线方程:x-y+1=0
2.记h(x)=e^x-x-1(x>=0),
那么h'(x)=e^x-1>=0,h(x)在x>=0递增
因此,h(x)>=h(0)=0,即得e^x>=x+1.
1.记y=f(x)=ax^2+bx+c,y=g(x)=e^x,那么
f'(x)=2ax+b,f''(x)=2a,g'(x)=g''(x)=e^x
根据题意,f(0)=g(0),f'(0)=g'(0),
f''(0)=g''(0)
有c=1,b=1,a=1/2,k=f'(0)=1
切线方程:x-y+1=0
2.记h(x)=e^x-x-1(x>=0),
那么h'(x)=e^x-1>=0,h(x)在x>=0递增
因此,h(x)>=h(0)=0,即得e^x>=x+1.