請問下列函數如何微分?

2016-01-08 11:34 am
1. y(x)={[(x^2+3x+2)^2][(x+5)^6][(x^2+3x+1)^4]}÷{(x^2)[(x+2)^3][(x+7)^4]}
2. h(x)=(x^2+3x+1)^(x^3+4x+1)

回答 (1)

2016-01-08 11:57 am
✔ 最佳答案
[ ln f(x) ]' = f'(x) / f(x)

1.
y(x) = (x² + 3x + 2)²(x + 5)⁶(x² + 3x + 1)⁴ ÷ [ x²(x + 2)³(x + 7)⁴

ln y(x) = ln { (x² + 3x + 2)²(x + 5)⁶(x² + 3x + 1)⁴ / [ x²(x + 2)³(x + 7)⁴ }
ln y(x) = 2 ln (x² + 3x + 2) + 6 ln (x + 5) + 4 ln (x² + 3x + 1) - 2 ln x - 3 ln (x + 2) - 4 ln (x + 7)

[ 1/y(x) ] y'(x) = 2(2x + 3)/(x² + 3x + 2) + 6/(x + 5) + 4(2x + 3)/(x² + 3x + 1) - 2/x - 3/(x + 2) - 4/(x + 7)

y'(x) = (x² + 3x + 2)²(x + 5)⁶(x² + 3x + 1)⁴/[ x²(x + 2)³(x + 7)⁴] [ 2(2x + 3)/(x² + 3x + 2) + 6/(x + 5) + 4(2x + 3)/(x² + 3x + 1) - 2/x - 3/(x + 2) - 4/(x + 7) ]

2.
h(x) = (x² + 3x + 1)^(x³ + 4x + 1)

ln h(x) = ln [ (x² + 3x + 1)^(x³ + 4x + 1) ]
ln h(x) = (x³ + 4x + 1) ln (x² + 3x + 1)

[ 1/h(x) ] h'(x) = (3x² + 4) ln (x² + 3x + 1) + (x³ + 4x + 1)(2x + 3)/(x² + 3x + 1)

h'(x) = [ (3x² + 4) ln (x² + 3x + 1) + (x³ + 4x + 1)(2x + 3)/(x² + 3x + 1) ] (x² + 3x + 1)^(x³ + 4x + 1)


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