I'm given x^3+y^3=6xy. It's stated that y is a function of x and I'm tasked to differentiate with respect to x.

Jaqueline Velez

Jaqueline Velez

Answered question

2022-09-27

I'm given x 3 + y 3 = 6 x y. It's stated that y is a function of x and I'm tasked to differentiate with respect to x.The implicit differentiation is:
3 x 2 + 3 y 2 y = 6 x y + 6 y
Now simplify and express in terms of y . I'm going to number these steps.
1. x 2 + y 2 y = 2 x y + 2 y
2. y = 2 x y + 2 y x 2 y 2
3. y = 2 x y y 2 + 2 y x 2 y 2
4. y = y 2 x y 2 + 2 y x 2 y 2
5. y y = 2 x y 2 + 2 y x 2 y 2 . We know that y y = 1 and therefore I've made a mistake in my algebra. But I'm not sure what is wrong.Here is the correct simplification, taking it from step 1 again:
1. x 2 + y 2 y = 2 x y + 2 y
2. y 2 y 2 x y = 2 y x 2
3. y ( y 2 2 x ) = 2 y x 2
4. y = 2 y x 2 y 2 2 x
This makes complete sense. What was wrong with my simplification? If it's not wrong, how can I arrive at the correct final expression of y ?

Answer & Explanation

Marley Stone

Marley Stone

Beginner2022-09-28Added 13 answers

Gather the y terms together to get y ( 6 x 3 y 2 ) = 3 x 2 6 y.
Then divide: y = 3 x 2 6 y 6 x 3 y 2 .

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