[求助] 化学狗求助求两线唯一交点已有2人参与

4楼: Originally posted by peterflyer at 2015-09-01 14:55:32
y=0.0701ln(x)+0.6429
100y=x+a
0.01*x+0.01*a=0.0701*lnx+0.6429
令F(x)=0.01*x+0.01*a-0.0701*lnx-0.6429
F'(x)=0.01-0.0701/x
令F ‘(x)=0解得驻点坐标 x=7.01
F''(x)=0.0701/x^2
故驻点处F取得最小值， ...

3楼: Originally posted by wurongjun at 2015-09-01 10:57:34
取切线情况!
切点x=7.01
>> x=100*0.0701
x =
    7.0100
>> y=0.0701*log(x)+0.6429
y =
    0.7794
>> a=100*y-x
a =
   70.9308