SOLUTION: Use the logarithmic differentiation to differentiate the function f(x)=∛((x^4 (x-2))/((x^2-2)(2x+3))) .

Algebra ->  Functions -> SOLUTION: Use the logarithmic differentiation to differentiate the function f(x)=∛((x^4 (x-2))/((x^2-2)(2x+3))) .       Log On


   



Question 1193108: Use the logarithmic differentiation to differentiate the function
f(x)=∛((x^4 (x-2))/((x^2-2)(2x+3))) .

Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
f%28x%29%22%22=%22%22%0D%0Aroot%283%2C%28x%5E4%28x%5E%22%22-2%29%29%2F%28%28x%5E2-2%29%282x%5E%22%22%2B3%29%29%29

Change the root to an fractional exponential

f%28x%29%22%22=%22%22

Take natural logs of both sides:

ln%28f%28x%29%5E%22%22%29%22%22=%22%22

Use the property of logarithms that allows us to
move the exponent (1/3) in front of the ln.

ln%28f%28x%29%5E%22%22%29%22%22=%22%22

Clear the fraction by multiplying both sides by 3

3%2Aln%28f%28x%29%5E%22%22%29%22%22=%22%22ln%28%0D%0A%28x%5E4%28x%5E%22%22-2%29%29%2F%28%28x%5E2-2%29%282x%5E%22%22%2B3%29%29%29

On the right side, write the log of a quotient as 
the log of the numerator minus the log of the 
denominator.

3%2Aln%28f%28x%29%5E%22%22%29%22%22=%22%22

On the right side, use the fact that the log of
a product is the sum of the logs: 

3%2Aln%28f%28x%29%5E%22%22%29%22%22=%22%22

On the right side write the 4 exponent in front of the log. 
Remove the largest parentheses:

3%2Aln%28f%28x%29%5E%22%22%29%22%22=%22%224%2Aln%28x%5E%22%22%29%2Bln%28x-2%5E%22%22%29-ln%28x%5E2-2%29-ln%282x%2B3%5E%22%22%29

Take the derivative of both sides, using:
The derivative of a natural log of an expression
is the derivative of the expression divided by
the expression:

3%2Aexpr%28%22f%27%28x%29%22%2Ff%28x%29%29%29%22%22=%22%22%22%22=%22%22

Put the 4 in the numerator in the first term on the right:

3%2Aexpr%28%22f%27%28x%29%22%2Ff%28x%29%29%29%22%22=%22%22%22%22=%22%22

Divide both sides by 3:

expr%28%22f%27%28x%29%22%2Ff%28x%29%29%29%22%22=%22%22%22%22=%22%22

Multiply both sides by f(x)

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Substitute for f(x) from the original equation

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Edwin