Calculus Examples

Find the Local Maxima and Minima f(x) = natural log of x^4+27
Step 1
Find the first derivative of the function.
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Step 1.1
Differentiate using the chain rule, which states that is where and .
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Step 1.1.1
To apply the Chain Rule, set as .
Step 1.1.2
The derivative of with respect to is .
Step 1.1.3
Replace all occurrences of with .
Step 1.2
Differentiate.
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Step 1.2.1
By the Sum Rule, the derivative of with respect to is .
Step 1.2.2
Differentiate using the Power Rule which states that is where .
Step 1.2.3
Since is constant with respect to , the derivative of with respect to is .
Step 1.2.4
Combine fractions.
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Step 1.2.4.1
Add and .
Step 1.2.4.2
Combine and .
Step 1.2.4.3
Combine and .
Step 2
Find the second derivative of the function.
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Step 2.1
Since is constant with respect to , the derivative of with respect to is .
Step 2.2
Differentiate using the Quotient Rule which states that is where and .
Step 2.3
Differentiate.
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Step 2.3.1
Differentiate using the Power Rule which states that is where .
Step 2.3.2
Move to the left of .
Step 2.3.3
By the Sum Rule, the derivative of with respect to is .
Step 2.3.4
Differentiate using the Power Rule which states that is where .
Step 2.3.5
Since is constant with respect to , the derivative of with respect to is .
Step 2.3.6
Simplify the expression.
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Step 2.3.6.1
Add and .
Step 2.3.6.2
Multiply by .
Step 2.4
Multiply by by adding the exponents.
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Step 2.4.1
Move .
Step 2.4.2
Use the power rule to combine exponents.
Step 2.4.3
Add and .
Step 2.5
Combine and .
Step 2.6
Simplify.
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Step 2.6.1
Apply the distributive property.
Step 2.6.2
Apply the distributive property.
Step 2.6.3
Apply the distributive property.
Step 2.6.4
Simplify the numerator.
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Step 2.6.4.1
Simplify each term.
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Step 2.6.4.1.1
Multiply by by adding the exponents.
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Step 2.6.4.1.1.1
Move .
Step 2.6.4.1.1.2
Use the power rule to combine exponents.
Step 2.6.4.1.1.3
Add and .
Step 2.6.4.1.2
Multiply by .
Step 2.6.4.1.3
Multiply by .
Step 2.6.4.1.4
Multiply by .
Step 2.6.4.1.5
Multiply by .
Step 2.6.4.2
Subtract from .
Step 3
To find the local maximum and minimum values of the function, set the derivative equal to and solve.
Step 4
Find the first derivative.
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Step 4.1
Find the first derivative.
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Step 4.1.1
Differentiate using the chain rule, which states that is where and .
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Step 4.1.1.1
To apply the Chain Rule, set as .
Step 4.1.1.2
The derivative of with respect to is .
Step 4.1.1.3
Replace all occurrences of with .
Step 4.1.2
Differentiate.
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Step 4.1.2.1
By the Sum Rule, the derivative of with respect to is .
Step 4.1.2.2
Differentiate using the Power Rule which states that is where .
Step 4.1.2.3
Since is constant with respect to , the derivative of with respect to is .
Step 4.1.2.4
Combine fractions.
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Step 4.1.2.4.1
Add and .
Step 4.1.2.4.2
Combine and .
Step 4.1.2.4.3
Combine and .
Step 4.2
The first derivative of with respect to is .
Step 5
Set the first derivative equal to then solve the equation .
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Step 5.1
Set the first derivative equal to .
Step 5.2
Set the numerator equal to zero.
Step 5.3
Solve the equation for .
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Step 5.3.1
Divide each term in by and simplify.
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Step 5.3.1.1
Divide each term in by .
Step 5.3.1.2
Simplify the left side.
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Step 5.3.1.2.1
Cancel the common factor of .
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Step 5.3.1.2.1.1
Cancel the common factor.
Step 5.3.1.2.1.2
Divide by .
Step 5.3.1.3
Simplify the right side.
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Step 5.3.1.3.1
Divide by .
Step 5.3.2
Take the specified root of both sides of the equation to eliminate the exponent on the left side.
Step 5.3.3
Simplify .
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Step 5.3.3.1
Rewrite as .
Step 5.3.3.2
Pull terms out from under the radical, assuming real numbers.
Step 6
Find the values where the derivative is undefined.
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Step 6.1
The domain of the expression is all real numbers except where the expression is undefined. In this case, there is no real number that makes the expression undefined.
Step 7
Critical points to evaluate.
Step 8
Evaluate the second derivative at . If the second derivative is positive, then this is a local minimum. If it is negative, then this is a local maximum.
Step 9
Evaluate the second derivative.
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Step 9.1
Simplify the numerator.
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Step 9.1.1
Raising to any positive power yields .
Step 9.1.2
Multiply by .
Step 9.1.3
Raising to any positive power yields .
Step 9.1.4
Multiply by .
Step 9.1.5
Add and .
Step 9.2
Simplify the denominator.
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Step 9.2.1
Raising to any positive power yields .
Step 9.2.2
Add and .
Step 9.2.3
Raise to the power of .
Step 9.3
Divide by .
Step 10
Since there is at least one point with or undefined second derivative, apply the first derivative test.
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Step 10.1
Split into separate intervals around the values that make the first derivative or undefined.
Step 10.2
Substitute any number, such as , from the interval in the first derivative to check if the result is negative or positive.
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Step 10.2.1
Replace the variable with in the expression.
Step 10.2.2
Simplify the result.
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Step 10.2.2.1
Raise to the power of .
Step 10.2.2.2
Simplify the denominator.
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Step 10.2.2.2.1
Raise to the power of .
Step 10.2.2.2.2
Add and .
Step 10.2.2.3
Simplify the expression.
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Step 10.2.2.3.1
Multiply by .
Step 10.2.2.3.2
Move the negative in front of the fraction.
Step 10.2.2.4
The final answer is .
Step 10.3
Substitute any number, such as , from the interval in the first derivative to check if the result is negative or positive.
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Step 10.3.1
Replace the variable with in the expression.
Step 10.3.2
Simplify the result.
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Step 10.3.2.1
Simplify the numerator.
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Step 10.3.2.1.1
Rewrite as .
Step 10.3.2.1.2
Use the power rule to combine exponents.
Step 10.3.2.1.3
Add and .
Step 10.3.2.2
Simplify the denominator.
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Step 10.3.2.2.1
Raise to the power of .
Step 10.3.2.2.2
Add and .
Step 10.3.2.3
Raise to the power of .
Step 10.3.2.4
The final answer is .
Step 10.4
Since the first derivative changed signs from negative to positive around , then is a local minimum.
is a local minimum
is a local minimum
Step 11