Implicit Differentiation Question

In summary, the problem involves finding dy/dx by implicit differentiation for the equation e^(x^2 * y) = x + y. The solution involves using the quotient rule and expanding the equation. The correct solution involves replacing x+y with e^(x^2 * y) in the final answer.
  • #1
RoyalFlush100
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Homework Statement


I am told to find dy/dx by implicit differentiation where:
e^(x^2 * y) = x + y

Homework Equations


The above equation and the ln of it.

The Attempt at a Solution


e^(x^2 * y) = x + y
(x^2 * y)ln(e) = ln(x+y)
x^2 * y = ln(x+y)
x^2(dy/dx) + y(2x) = 1/(x+y) * (1 + dy/dx)
(dy/dx)[x^2 - 1/(x+y)] = 1/(x+y) - 2xy
dy/dx = (1/(x+y) - 2xy)/(x^2 - 1/(x+y))

or here: https://postimg.org/image/3k5ygbkxt/

This was marked wrong (online software). It doesn't care about simplest form and it was entered properly. So, what did I do wrong?
 

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  • #2
I got the same result without using the logarithm, only with a single quotient, i.e. expanded by ##x+y##. Maybe the missing brackets in your linear notation led to the online error. Or it is expected to write ##e^{x^2y}## instead of ##x+y## in the solution.
 
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  • #3
fresh_42 said:
I got the same result without using the logarithm, only with a single quotient, i.e. expanded by ##x+y##. Maybe the missing brackets in your linear notation led to the online error. Or it is expected to write ##e^{x^2y}## instead of ##x+y## in the solution.

I just put it in replacing x+y with e^(x^2 * y) and it worked. Thanks!
 
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1. What is implicit differentiation?

Implicit differentiation is a mathematical technique used to find the derivative of a function that is not explicitly expressed in terms of the independent variable. This means that the equation may not be in the form of y = f(x), but instead may be in the form of an equation with both x and y variables. Implicit differentiation allows us to find the slope of the curve at any point without having to solve for y explicitly.

2. When is implicit differentiation used?

Implicit differentiation is used when we have a function that is not explicitly defined in terms of the independent variable or when it is difficult or impossible to solve for y explicitly. This method is particularly useful when dealing with more complex equations such as circles, ellipses, and curves.

3. How is implicit differentiation different from explicit differentiation?

In explicit differentiation, the derivative is found by solving for y explicitly in terms of x and then taking the derivative. However, in implicit differentiation, we do not solve for y explicitly and instead use the rules of differentiation to find the derivative of both x and y with respect to each other.

4. What are the steps for implicit differentiation?

The steps for implicit differentiation are as follows:
1. Differentiate both sides of the equation with respect to x
2. Apply the chain rule for any terms that involve y
3. Isolate the dy/dx term on one side of the equation
4. Solve for dy/dx to find the derivative

5. What are some common mistakes when using implicit differentiation?

Some common mistakes when using implicit differentiation include forgetting to apply the chain rule, incorrectly simplifying the equation, and mixing up the order of the variables when taking the derivative. It is important to carefully follow the steps and double check your work to avoid these mistakes.

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