Calculus Examples

Use the Limit Definition to Find the Derivative f(x)=x^2e^(-x)
Step 1
Consider the limit definition of the derivative.
Step 2
Find the components of the definition.
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Step 2.1
Evaluate the function at .
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Step 2.1.1
Replace the variable with in the expression.
Step 2.1.2
Simplify the result.
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Step 2.1.2.1
Rewrite as .
Step 2.1.2.2
Expand using the FOIL Method.
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Step 2.1.2.2.1
Apply the distributive property.
Step 2.1.2.2.2
Apply the distributive property.
Step 2.1.2.2.3
Apply the distributive property.
Step 2.1.2.3
Simplify and combine like terms.
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Step 2.1.2.3.1
Simplify each term.
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Step 2.1.2.3.1.1
Multiply by .
Step 2.1.2.3.1.2
Multiply by .
Step 2.1.2.3.2
Add and .
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Step 2.1.2.3.2.1
Reorder and .
Step 2.1.2.3.2.2
Add and .
Step 2.1.2.4
Apply the distributive property.
Step 2.1.2.5
Apply the distributive property.
Step 2.1.2.6
The final answer is .
Step 2.2
Reorder.
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Step 2.2.1
Reorder and .
Step 2.2.2
Reorder and .
Step 2.2.3
Reorder and .
Step 2.3
Find the components of the definition.
Step 3
Plug in the components.
Step 4
Remove parentheses.
Step 5
Apply L'Hospital's rule.
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Step 5.1
Evaluate the limit of the numerator and the limit of the denominator.
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Step 5.1.1
Take the limit of the numerator and the limit of the denominator.
Step 5.1.2
Evaluate the limit of the numerator.
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Step 5.1.2.1
Split the limit using the Sum of Limits Rule on the limit as approaches .
Step 5.1.2.2
Move the term outside of the limit because it is constant with respect to .
Step 5.1.2.3
Move the limit into the exponent.
Step 5.1.2.4
Split the limit using the Sum of Limits Rule on the limit as approaches .
Step 5.1.2.5
Evaluate the limit of which is constant as approaches .
Step 5.1.2.6
Move the term outside of the limit because it is constant with respect to .
Step 5.1.2.7
Split the limit using the Product of Limits Rule on the limit as approaches .
Step 5.1.2.8
Move the limit into the exponent.
Step 5.1.2.9
Split the limit using the Sum of Limits Rule on the limit as approaches .
Step 5.1.2.10
Evaluate the limit of which is constant as approaches .
Step 5.1.2.11
Split the limit using the Product of Limits Rule on the limit as approaches .
Step 5.1.2.12
Move the exponent from outside the limit using the Limits Power Rule.
Step 5.1.2.13
Move the limit into the exponent.
Step 5.1.2.14
Split the limit using the Sum of Limits Rule on the limit as approaches .
Step 5.1.2.15
Evaluate the limit of which is constant as approaches .
Step 5.1.2.16
Evaluate the limit of which is constant as approaches .
Step 5.1.2.17
Evaluate the limits by plugging in for all occurrences of .
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Step 5.1.2.17.1
Evaluate the limit of by plugging in for .
Step 5.1.2.17.2
Evaluate the limit of by plugging in for .
Step 5.1.2.17.3
Evaluate the limit of by plugging in for .
Step 5.1.2.17.4
Evaluate the limit of by plugging in for .
Step 5.1.2.17.5
Evaluate the limit of by plugging in for .
Step 5.1.2.18
Simplify the answer.
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Step 5.1.2.18.1
Combine the opposite terms in .
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Step 5.1.2.18.1.1
Subtract from .
Step 5.1.2.18.1.2
Subtract from .
Step 5.1.2.18.1.3
Subtract from .
Step 5.1.2.18.1.4
Subtract from .
Step 5.1.2.18.1.5
Add and .
Step 5.1.2.18.2
Simplify each term.
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Step 5.1.2.18.2.1
Multiply .
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Step 5.1.2.18.2.1.1
Multiply by .
Step 5.1.2.18.2.1.2
Multiply by .
Step 5.1.2.18.2.2
Multiply by .
Step 5.1.2.18.2.3
Raising to any positive power yields .
Step 5.1.2.18.2.4
Multiply by .
Step 5.1.2.18.3
Add and .
Step 5.1.3
Evaluate the limit of by plugging in for .
Step 5.1.4
The expression contains a division by . The expression is undefined.
Undefined
Step 5.2
Since is of indeterminate form, apply L'Hospital's Rule. L'Hospital's Rule states that the limit of a quotient of functions is equal to the limit of the quotient of their derivatives.
Step 5.3
Find the derivative of the numerator and denominator.
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Step 5.3.1
Differentiate the numerator and denominator.
Step 5.3.2
By the Sum Rule, the derivative of with respect to is .
Step 5.3.3
Evaluate .
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Step 5.3.3.1
Since is constant with respect to , the derivative of with respect to is .
Step 5.3.3.2
Differentiate using the chain rule, which states that is where and .
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Step 5.3.3.2.1
To apply the Chain Rule, set as .
Step 5.3.3.2.2
Differentiate using the Exponential Rule which states that is where =.
Step 5.3.3.2.3
Replace all occurrences of with .
Step 5.3.3.3
By the Sum Rule, the derivative of with respect to is .
Step 5.3.3.4
Since is constant with respect to , the derivative of with respect to is .
Step 5.3.3.5
Differentiate using the Power Rule which states that is where .
Step 5.3.3.6
Since is constant with respect to , the derivative of with respect to is .
Step 5.3.3.7
Multiply by .
Step 5.3.3.8
Add and .
Step 5.3.3.9
Move to the left of .
Step 5.3.3.10
Rewrite as .
Step 5.3.4
Evaluate .
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Step 5.3.4.1
Since is constant with respect to , the derivative of with respect to is .
Step 5.3.4.2
Differentiate using the Product Rule which states that is where and .
Step 5.3.4.3
Differentiate using the chain rule, which states that is where and .
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Step 5.3.4.3.1
To apply the Chain Rule, set as .
Step 5.3.4.3.2
Differentiate using the Exponential Rule which states that is where =.
Step 5.3.4.3.3
Replace all occurrences of with .
Step 5.3.4.4
By the Sum Rule, the derivative of with respect to is .
Step 5.3.4.5
Since is constant with respect to , the derivative of with respect to is .
Step 5.3.4.6
Differentiate using the Power Rule which states that is where .
Step 5.3.4.7
Since is constant with respect to , the derivative of with respect to is .
Step 5.3.4.8
Differentiate using the Power Rule which states that is where .
Step 5.3.4.9
Multiply by .
Step 5.3.4.10
Add and .
Step 5.3.4.11
Move to the left of .
Step 5.3.4.12
Rewrite as .
Step 5.3.4.13
Multiply by .
Step 5.3.5
Evaluate .
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Step 5.3.5.1
Differentiate using the Product Rule which states that is where and .
Step 5.3.5.2
Differentiate using the chain rule, which states that is where and .
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Step 5.3.5.2.1
To apply the Chain Rule, set as .
Step 5.3.5.2.2
Differentiate using the Exponential Rule which states that is where =.
Step 5.3.5.2.3
Replace all occurrences of with .
Step 5.3.5.3
By the Sum Rule, the derivative of with respect to is .
Step 5.3.5.4
Since is constant with respect to , the derivative of with respect to is .
Step 5.3.5.5
Differentiate using the Power Rule which states that is where .
Step 5.3.5.6
Since is constant with respect to , the derivative of with respect to is .
Step 5.3.5.7
Differentiate using the Power Rule which states that is where .
Step 5.3.5.8
Multiply by .
Step 5.3.5.9
Add and .
Step 5.3.5.10
Move to the left of .
Step 5.3.5.11
Rewrite as .
Step 5.3.6
Since is constant with respect to , the derivative of with respect to is .
Step 5.3.7
Simplify.
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Step 5.3.7.1
Apply the distributive property.
Step 5.3.7.2
Combine terms.
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Step 5.3.7.2.1
Multiply by .
Step 5.3.7.2.2
Add and .
Step 5.3.7.3
Reorder terms.
Step 5.3.7.4
Reorder factors in .
Step 5.3.8
Differentiate using the Power Rule which states that is where .
Step 5.4
Divide by .
Step 6
Evaluate the limit.
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Step 6.1
Split the limit using the Sum of Limits Rule on the limit as approaches .
Step 6.2
Move the term outside of the limit because it is constant with respect to .
Step 6.3
Move the limit into the exponent.
Step 6.4
Split the limit using the Sum of Limits Rule on the limit as approaches .
Step 6.5
Evaluate the limit of which is constant as approaches .
Step 6.6
Move the term outside of the limit because it is constant with respect to .
Step 6.7
Split the limit using the Product of Limits Rule on the limit as approaches .
Step 6.8
Move the limit into the exponent.
Step 6.9
Split the limit using the Sum of Limits Rule on the limit as approaches .
Step 6.10
Evaluate the limit of which is constant as approaches .
Step 6.11
Move the term outside of the limit because it is constant with respect to .
Step 6.12
Move the limit into the exponent.
Step 6.13
Split the limit using the Sum of Limits Rule on the limit as approaches .
Step 6.14
Evaluate the limit of which is constant as approaches .
Step 6.15
Split the limit using the Product of Limits Rule on the limit as approaches .
Step 6.16
Move the exponent from outside the limit using the Limits Power Rule.
Step 6.17
Move the limit into the exponent.
Step 6.18
Split the limit using the Sum of Limits Rule on the limit as approaches .
Step 6.19
Evaluate the limit of which is constant as approaches .
Step 6.20
Move the term outside of the limit because it is constant with respect to .
Step 6.21
Split the limit using the Product of Limits Rule on the limit as approaches .
Step 6.22
Move the limit into the exponent.
Step 6.23
Split the limit using the Sum of Limits Rule on the limit as approaches .
Step 6.24
Evaluate the limit of which is constant as approaches .
Step 7
Evaluate the limits by plugging in for all occurrences of .
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Step 7.1
Evaluate the limit of by plugging in for .
Step 7.2
Evaluate the limit of by plugging in for .
Step 7.3
Evaluate the limit of by plugging in for .
Step 7.4
Evaluate the limit of by plugging in for .
Step 7.5
Evaluate the limit of by plugging in for .
Step 7.6
Evaluate the limit of by plugging in for .
Step 7.7
Evaluate the limit of by plugging in for .
Step 7.8
Evaluate the limit of by plugging in for .
Step 8
Simplify the answer.
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Step 8.1
Combine the opposite terms in .
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Step 8.1.1
Subtract from .
Step 8.1.2
Subtract from .
Step 8.1.3
Subtract from .
Step 8.1.4
Subtract from .
Step 8.1.5
Subtract from .
Step 8.2
Simplify each term.
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Step 8.2.1
Multiply by .
Step 8.2.2
Multiply .
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Step 8.2.2.1
Multiply by .
Step 8.2.2.2
Multiply by .
Step 8.2.3
Multiply by .
Step 8.2.4
Raising to any positive power yields .
Step 8.2.5
Multiply by .
Step 8.2.6
Multiply by .
Step 8.2.7
Multiply by .
Step 8.2.8
Multiply by .
Step 8.3
Combine the opposite terms in .
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Step 8.3.1
Add and .
Step 8.3.2
Add and .
Step 8.3.3
Add and .
Step 9