Calculus Examples

Find the Local Maxima and Minima f(x)=3x^4+4x^3-48x^2-144x+288
Step 1
Find the first derivative of the function.
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Step 1.1
By the Sum Rule, the derivative of with respect to is .
Step 1.2
Evaluate .
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Step 1.2.1
Since is constant with respect to , 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
Multiply by .
Step 1.3
Evaluate .
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Step 1.3.1
Since is constant with respect to , the derivative of with respect to is .
Step 1.3.2
Differentiate using the Power Rule which states that is where .
Step 1.3.3
Multiply by .
Step 1.4
Evaluate .
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Step 1.4.1
Since is constant with respect to , the derivative of with respect to is .
Step 1.4.2
Differentiate using the Power Rule which states that is where .
Step 1.4.3
Multiply by .
Step 1.5
Evaluate .
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Step 1.5.1
Since is constant with respect to , the derivative of with respect to is .
Step 1.5.2
Differentiate using the Power Rule which states that is where .
Step 1.5.3
Multiply by .
Step 1.6
Differentiate using the Constant Rule.
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Step 1.6.1
Since is constant with respect to , the derivative of with respect to is .
Step 1.6.2
Add and .
Step 2
Find the second derivative of the function.
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Step 2.1
By the Sum Rule, the derivative of with respect to is .
Step 2.2
Evaluate .
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Step 2.2.1
Since is constant with respect to , the derivative of with respect to is .
Step 2.2.2
Differentiate using the Power Rule which states that is where .
Step 2.2.3
Multiply by .
Step 2.3
Evaluate .
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Step 2.3.1
Since is constant with respect to , the derivative of with respect to is .
Step 2.3.2
Differentiate using the Power Rule which states that is where .
Step 2.3.3
Multiply by .
Step 2.4
Evaluate .
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Step 2.4.1
Since is constant with respect to , the derivative of with respect to is .
Step 2.4.2
Differentiate using the Power Rule which states that is where .
Step 2.4.3
Multiply by .
Step 2.5
Differentiate using the Constant Rule.
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Step 2.5.1
Since is constant with respect to , the derivative of with respect to is .
Step 2.5.2
Add and .
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
By the Sum Rule, the derivative of with respect to is .
Step 4.1.2
Evaluate .
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Step 4.1.2.1
Since is constant with respect to , 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
Multiply by .
Step 4.1.3
Evaluate .
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Step 4.1.3.1
Since is constant with respect to , the derivative of with respect to is .
Step 4.1.3.2
Differentiate using the Power Rule which states that is where .
Step 4.1.3.3
Multiply by .
Step 4.1.4
Evaluate .
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Step 4.1.4.1
Since is constant with respect to , the derivative of with respect to is .
Step 4.1.4.2
Differentiate using the Power Rule which states that is where .
Step 4.1.4.3
Multiply by .
Step 4.1.5
Evaluate .
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Step 4.1.5.1
Since is constant with respect to , the derivative of with respect to is .
Step 4.1.5.2
Differentiate using the Power Rule which states that is where .
Step 4.1.5.3
Multiply by .
Step 4.1.6
Differentiate using the Constant Rule.
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Step 4.1.6.1
Since is constant with respect to , the derivative of with respect to is .
Step 4.1.6.2
Add 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
Factor the left side of the equation.
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Step 5.2.1
Factor out of .
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Step 5.2.1.1
Factor out of .
Step 5.2.1.2
Factor out of .
Step 5.2.1.3
Factor out of .
Step 5.2.1.4
Factor out of .
Step 5.2.1.5
Factor out of .
Step 5.2.1.6
Factor out of .
Step 5.2.1.7
Factor out of .
Step 5.2.2
Factor using the rational roots test.
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Step 5.2.2.1
If a polynomial function has integer coefficients, then every rational zero will have the form where is a factor of the constant and is a factor of the leading coefficient.
Step 5.2.2.2
Find every combination of . These are the possible roots of the polynomial function.
Step 5.2.2.3
Substitute and simplify the expression. In this case, the expression is equal to so is a root of the polynomial.
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Step 5.2.2.3.1
Substitute into the polynomial.
Step 5.2.2.3.2
Raise to the power of .
Step 5.2.2.3.3
Raise to the power of .
Step 5.2.2.3.4
Add and .
Step 5.2.2.3.5
Multiply by .
Step 5.2.2.3.6
Add and .
Step 5.2.2.3.7
Subtract from .
Step 5.2.2.4
Since is a known root, divide the polynomial by to find the quotient polynomial. This polynomial can then be used to find the remaining roots.
Step 5.2.2.5
Divide by .
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Step 5.2.2.5.1
Set up the polynomials to be divided. If there is not a term for every exponent, insert one with a value of .
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Step 5.2.2.5.2
Divide the highest order term in the dividend by the highest order term in divisor .
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Step 5.2.2.5.3
Multiply the new quotient term by the divisor.
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++
Step 5.2.2.5.4
The expression needs to be subtracted from the dividend, so change all the signs in
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--
Step 5.2.2.5.5
After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.
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--
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Step 5.2.2.5.6
Pull the next terms from the original dividend down into the current dividend.
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Step 5.2.2.5.7
Divide the highest order term in the dividend by the highest order term in divisor .
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Step 5.2.2.5.8
Multiply the new quotient term by the divisor.
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Step 5.2.2.5.9
The expression needs to be subtracted from the dividend, so change all the signs in
-
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++
Step 5.2.2.5.10
After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.
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++--
--
--
++
-
Step 5.2.2.5.11
Pull the next terms from the original dividend down into the current dividend.
-
++--
--
--
++
--
Step 5.2.2.5.12
Divide the highest order term in the dividend by the highest order term in divisor .
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--
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++
--
Step 5.2.2.5.13
Multiply the new quotient term by the divisor.
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--
Step 5.2.2.5.14
The expression needs to be subtracted from the dividend, so change all the signs in
--
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++
Step 5.2.2.5.15
After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.
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++
Step 5.2.2.5.16
Since the remander is , the final answer is the quotient.
Step 5.2.2.6
Write as a set of factors.
Step 5.2.3
Factor.
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Step 5.2.3.1
Factor using the AC method.
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Step 5.2.3.1.1
Factor using the AC method.
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Step 5.2.3.1.1.1
Consider the form . Find a pair of integers whose product is and whose sum is . In this case, whose product is and whose sum is .
Step 5.2.3.1.1.2
Write the factored form using these integers.
Step 5.2.3.1.2
Remove unnecessary parentheses.
Step 5.2.3.2
Remove unnecessary parentheses.
Step 5.2.4
Combine exponents.
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Step 5.2.4.1
Raise to the power of .
Step 5.2.4.2
Raise to the power of .
Step 5.2.4.3
Use the power rule to combine exponents.
Step 5.2.4.4
Add and .
Step 5.3
If any individual factor on the left side of the equation is equal to , the entire expression will be equal to .
Step 5.4
Set equal to and solve for .
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Step 5.4.1
Set equal to .
Step 5.4.2
Solve for .
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Step 5.4.2.1
Set the equal to .
Step 5.4.2.2
Subtract from both sides of the equation.
Step 5.5
Set equal to and solve for .
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Step 5.5.1
Set equal to .
Step 5.5.2
Add to both sides of the equation.
Step 5.6
The final solution is all the values that make true.
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 each term.
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Step 9.1.1
Raise to the power of .
Step 9.1.2
Multiply by .
Step 9.1.3
Multiply by .
Step 9.2
Simplify by subtracting numbers.
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Step 9.2.1
Subtract from .
Step 9.2.2
Subtract from .
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
Simplify each term.
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Step 10.2.2.1.1
Raise to the power of .
Step 10.2.2.1.2
Multiply by .
Step 10.2.2.1.3
Raise to the power of .
Step 10.2.2.1.4
Multiply by .
Step 10.2.2.1.5
Multiply by .
Step 10.2.2.2
Simplify by adding and subtracting.
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Step 10.2.2.2.1
Add and .
Step 10.2.2.2.2
Add and .
Step 10.2.2.2.3
Subtract from .
Step 10.2.2.3
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 each term.
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Step 10.3.2.1.1
Raising to any positive power yields .
Step 10.3.2.1.2
Multiply by .
Step 10.3.2.1.3
Raising to any positive power yields .
Step 10.3.2.1.4
Multiply by .
Step 10.3.2.1.5
Multiply by .
Step 10.3.2.2
Simplify by adding and subtracting.
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Step 10.3.2.2.1
Add and .
Step 10.3.2.2.2
Add and .
Step 10.3.2.2.3
Subtract from .
Step 10.3.2.3
The final answer is .
Step 10.4
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 10.4.1
Replace the variable with in the expression.
Step 10.4.2
Simplify the result.
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Step 10.4.2.1
Simplify each term.
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Step 10.4.2.1.1
Raise to the power of .
Step 10.4.2.1.2
Multiply by .
Step 10.4.2.1.3
Raise to the power of .
Step 10.4.2.1.4
Multiply by .
Step 10.4.2.1.5
Multiply by .
Step 10.4.2.2
Simplify by adding and subtracting.
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Step 10.4.2.2.1
Add and .
Step 10.4.2.2.2
Subtract from .
Step 10.4.2.2.3
Subtract from .
Step 10.4.2.3
The final answer is .
Step 10.5
Since the first derivative did not change signs around , this is not a local maximum or minimum.
Not a local maximum or minimum
Step 10.6
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