求y=[x+(x^2+24)^(1/2)]^(1/3)的導

2011-08-27 9:27 am
求 y = [x + (x^2 + 24)^(1/2)]^(1/3) 的導數。

THX!

回答 (1)

2011-08-27 4:56 pm
✔ 最佳答案
y = [x + (x^2 + 24)^(1/2)]^(1/3)
y = t^1/3
t = x + (x^2 + 24)^(1/2)

dy/dt = (1/3)t^(-2/3)
dt/dx =1 +(1/2)(x^2 + 24)^(-1/2)d/dx(x^2 + 24)
dt/dx =1 +(1/2)(x^2 + 24)^(-1/2)(2x)
dt/dx =1 +x(x^2 + 24)^(-1/2)

dy/dx =( dy/dt)(dt/dx)
dy/dx = (1/3)t^(-2/3) [1 +x(x^2 + 24)^(-1/2)]
dy/dx = (1/3)[ x + (x^2 + 24)^(1/2)]^(-2/3) [1 +x(x^2 + 24)^(-1/2)]


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