作者a88241050 (难道阿宅错了吗)
看板trans_math
标题Re: [微分] 切线问题
时间Sun Dec 6 17:34:11 2009
※ 引述《di7101483 (新生代)》之铭言：
: Find the points on the graph of y=x^5/3+x^1/3 at which the tangent line is
: perpendicular to the line 2y+x=7
: 这题的方程式怎麽那麽难解
y'=5/3*x^(2/3)+1/3*x(-2/3) = 2
5x^(2/3)+x^(-2/3)=6
令x^(2/3)=z
:5z+1/z=6
5z^2-6z+1=0
(5z-1)(z-1)=0
z=1/5,1
x=5^(-3/2), 1
y=26根号5/125, 2
(5^(-3/2),26根号5/125) , (1,2)
--
--
※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 140.135.32.98
※ 编辑: a88241050 来自: 140.135.32.98 (12/06 17:40)