兩邊取對(duì)數(shù)得
ln(y) = ln(t) / 2 - ln(t+1) /2
兩邊對(duì)t求導(dǎo),由鏈?zhǔn)椒▌t：
{ln(y)]' = 1/y * y' = 1/(2t) - 1/(2t+2) = 1 / [2(t+1)t]
所以y' = y/[2(t+1)t] = 1/(2*t^(1/2))(t+1)^3/2