Maths Help Evaluate f''(x)?

2016-11-29 7:52 am

回答 (1)

2016-11-29 9:21 am
✔ 最佳答案
Sol
y=x^(3/2)/(x^2+1)
yx^2+y=x^(3/2)
2xy+x^2y’+y’=(3/2)x^(1/2)
(x^2+1)y’=(3/2)x^(1/2)-2xy
=(3/2)x^(1/2)-2x*x^(3/2)/(x^2+1)
=(3/2)x^(1/2)-2x^(5/2)/(x^2+1)
y’=(3/2)x^(1/2)/(x^2+1)-2x^(5/2)/(x^2+1)^2
(x^2+1)y’=(3/2)x^(1/2)-2xy
(x^2+1)y”+2xy’=(3/4)x^(-1/2)-2xy’-2y
(x^2+1)y”=(3/4)x^(-1/2)-4xy’-2y
=(3/4)x^(-1/2)-4x*[(3/2)x^(1/2)/(x^2+1)-2x^(5/2)/(x^2+1)^2]
-2x^(3/2)/(x^2+1)
=(3/4)x^(-1/2)-6x^(3/2)/(x^2+1)-8x^(7/2)/(x^2+1)^2-2x^(3/2)/(x^2+1)
=(3/4)x^(-1/2)-8x^(3/2)/(x^2+1)-8x^(7/2)/(x^2+1)^2
y”=(3/4)x^(-1/2)/(x^2+1)-8x^(3/2)/(x^2+1)^2-8x^(7/2)/(x^2+1)^3


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