implicit differentiation, part 2

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In this presentation we solve two more examples of implicit differentiation problems. We use a faster, more direct method. For more lessons visit: http://www.intuitive-calculus.com/implicit-differentiation.html

TRANSCRIPT

Example 2

Example 2

Let’s find y ′ given that:

Example 2

Let’s find y ′ given that:

4x2y − 5y = x3

Example 2

Let’s find y ′ given that:

4x2y − 5y = x3

First, we apply the derivative to both sides:

Example 2

Let’s find y ′ given that:

4x2y − 5y = x3

First, we apply the derivative to both sides:

d

dx

[4x2y − 5y

]=

d

dx

(x3)

Example 2

Let’s find y ′ given that:

4x2y − 5y = x3

First, we apply the derivative to both sides:

d

dx

[4x2y − 5y

]=

d

dx

(x3)

d

dx

(4x2y

)− 5

dy

dx=

d

dx

(x3)

Example 2

Let’s find y ′ given that:

4x2y − 5y = x3

First, we apply the derivative to both sides:

d

dx

[4x2y − 5y

]=

d

dx

(x3)

d

dx

(4x2y

)︸ ︷︷ ︸product rule!

−5dy

dx=

d

dx

(x3)

Example 2

Let’s find y ′ given that:

4x2y − 5y = x3

First, we apply the derivative to both sides:

d

dx

[4x2y − 5y

]=

d

dx

(x3)

d

dx

(4x2y

)︸ ︷︷ ︸product rule!

−5����y ′

dy

dx=

d

dx

(x3)

Example 2

Let’s find y ′ given that:

4x2y − 5y = x3

First, we apply the derivative to both sides:

d

dx

[4x2y − 5y

]=

d

dx

(x3)

d

dx

(4x2y

)︸ ︷︷ ︸product rule!

−5����y ′

dy

dx=�����>

3x2

d

dx

(x3)

Example 2

Let’s find y ′ given that:

4x2y − 5y = x3

First, we apply the derivative to both sides:

d

dx

[4x2y − 5y

]=

d

dx

(x3)

d

dx

(4x2y

)︸ ︷︷ ︸product rule!

−5����y ′

dy

dx=�����>

3x2

d

dx

(x3)

Here we apply the product rule:

Example 2

Let’s find y ′ given that:

4x2y − 5y = x3

First, we apply the derivative to both sides:

d

dx

[4x2y − 5y

]=

d

dx

(x3)

d

dx

(4x2y

)︸ ︷︷ ︸product rule!

−5����y ′

dy

dx=�����>

3x2

d

dx

(x3)

Here we apply the product rule:

4.

Example 2

Let’s find y ′ given that:

4x2y − 5y = x3

First, we apply the derivative to both sides:

d

dx

[4x2y − 5y

]=

d

dx

(x3)

d

dx

(4x2y

)︸ ︷︷ ︸product rule!

−5����y ′

dy

dx=�����>

3x2

d

dx

(x3)

Here we apply the product rule:

4.(2x).

Example 2

Let’s find y ′ given that:

4x2y − 5y = x3

First, we apply the derivative to both sides:

d

dx

[4x2y − 5y

]=

d

dx

(x3)

d

dx

(4x2y

)︸ ︷︷ ︸product rule!

−5����y ′

dy

dx=�����>

3x2

d

dx

(x3)

Here we apply the product rule:

4.(2x).y+

Example 2

Let’s find y ′ given that:

4x2y − 5y = x3

First, we apply the derivative to both sides:

d

dx

[4x2y − 5y

]=

d

dx

(x3)

d

dx

(4x2y

)︸ ︷︷ ︸product rule!

−5����y ′

dy

dx=�����>

3x2

d

dx

(x3)

Here we apply the product rule:

4.(2x).y + 4x2.

Example 2

Let’s find y ′ given that:

4x2y − 5y = x3

First, we apply the derivative to both sides:

d

dx

[4x2y − 5y

]=

d

dx

(x3)

d

dx

(4x2y

)︸ ︷︷ ︸product rule!

−5����y ′

dy

dx=�����>

3x2

d

dx

(x3)

Here we apply the product rule:

4.(2x).y + 4x2.y ′−

Example 2

Let’s find y ′ given that:

4x2y − 5y = x3

First, we apply the derivative to both sides:

d

dx

[4x2y − 5y

]=

d

dx

(x3)

d

dx

(4x2y

)︸ ︷︷ ︸product rule!

−5����y ′

dy

dx=�����>

3x2

d

dx

(x3)

Here we apply the product rule:

4.(2x).y + 4x2.y ′ − 5y ′ =

Example 2

Let’s find y ′ given that:

4x2y − 5y = x3

First, we apply the derivative to both sides:

d

dx

[4x2y − 5y

]=

d

dx

(x3)

d

dx

(4x2y

)︸ ︷︷ ︸product rule!

−5����y ′

dy

dx=�����>

3x2

d

dx

(x3)

Here we apply the product rule:

4.(2x).y + 4x2.y ′ − 5y ′ = 3x2

Example 2

Example 2

We have the relation:

Example 2

We have the relation:

8xy + 4x2y ′ − 5y ′ = 3x2

Example 2

We have the relation:

8xy + 4x2y ′ − 5y ′ = 3x2

We only need to solve for y ′:

Example 2

We have the relation:

8xy + 4x2y ′ − 5y ′ = 3x2

We only need to solve for y ′:

y ′(4x2 − 5

)= 3x2 − 8xy

Example 2

We have the relation:

8xy + 4x2y ′ − 5y ′ = 3x2

We only need to solve for y ′:

y ′(4x2 − 5

)= 3x2 − 8xy

y ′ =3x2 − 8xy

4x2 − 5

Example 2

We have the relation:

8xy + 4x2y ′ − 5y ′ = 3x2

We only need to solve for y ′:

y ′(4x2 − 5

)= 3x2 − 8xy

y ′ =3x2 − 8xy

4x2 − 5

Example 3

Example 3

Let’s consider the equation:

Example 3

Let’s consider the equation:

x23 + y

23 = a

23

Example 3

Let’s consider the equation:

x23 + y

23 = a

23

Let’s find y ′:

Example 3

Let’s consider the equation:

x23 + y

23 = a

23

Let’s find y ′:

d

dx

[x

23 + y

23

]=

d

dx

(a

23

)

Example 3

Let’s consider the equation:

x23 + y

23 = a

23

Let’s find y ′:

d

dx

[x

23 + y

23

]=��

���*

0d

dx

(a

23

)

Example 3

Let’s consider the equation:

x23 + y

23 = a

23

Let’s find y ′:

d

dx

[x

23 + y

23

]=��

���*

0d

dx

(a

23

)d

dx

(x

23

)+

d

dx

(y

23

)= 0

Example 3

Let’s consider the equation:

x23 + y

23 = a

23

Let’s find y ′:

d

dx

[x

23 + y

23

]=��

���*

0d

dx

(a

23

)d

dx

(x

23

)+

d

dx

(y

23

)= 0

Here we apply the chain rule:

Example 3

Let’s consider the equation:

x23 + y

23 = a

23

Let’s find y ′:

d

dx

[x

23 + y

23

]=��

���*

0d

dx

(a

23

)d

dx

(x

23

)+

d

dx

(y

23

)= 0

Here we apply the chain rule:

2

3.

Example 3

Let’s consider the equation:

x23 + y

23 = a

23

Let’s find y ′:

d

dx

[x

23 + y

23

]=��

���*

0d

dx

(a

23

)d

dx

(x

23

)+

d

dx

(y

23

)= 0

Here we apply the chain rule:

2

3.x

23−1+

Example 3

Let’s consider the equation:

x23 + y

23 = a

23

Let’s find y ′:

d

dx

[x

23 + y

23

]=��

���*

0d

dx

(a

23

)d

dx

(x

23

)+

d

dx

(y

23

)= 0

Here we apply the chain rule:

2

3.x

23−1 +

2

3.

Example 3

Let’s consider the equation:

x23 + y

23 = a

23

Let’s find y ′:

d

dx

[x

23 + y

23

]=��

���*

0d

dx

(a

23

)d

dx

(x

23

)+

d

dx

(y

23

)= 0

Here we apply the chain rule:

2

3.x

23−1 +

2

3.y

23−1.

Example 3

Let’s consider the equation:

x23 + y

23 = a

23

Let’s find y ′:

d

dx

[x

23 + y

23

]=��

���*

0d

dx

(a

23

)d

dx

(x

23

)+

d

dx

(y

23

)= 0

Here we apply the chain rule:

2

3.x

23−1 +

2

3.y

23−1.y ′ = 0

Example 3

Let’s consider the equation:

x23 + y

23 = a

23

Let’s find y ′:

d

dx

[x

23 + y

23

]=��

���*

0d

dx

(a

23

)d

dx

(x

23

)+

d

dx

(y

23

)= 0

Here we apply the chain rule:

2

3.x

23−1 +

2

3.y

23−1.y ′ = 0

2

3.x−

13 +

2

3.y−

13 .y ′ = 0

Example 3

Let’s consider the equation:

x23 + y

23 = a

23

Let’s find y ′:

d

dx

[x

23 + y

23

]=��

���*

0d

dx

(a

23

)d

dx

(x

23

)+

d

dx

(y

23

)= 0

Here we apply the chain rule:

2

3.x

23−1 +

2

3.y

23−1.y ′ = 0

���2

3.x−

13 +���2

3.y−

13 .y ′ = 0

Example 3

Example 3

We now have the equation:

Example 3

We now have the equation:

x−13 + y−

13 y ′ = 0

Example 3

We now have the equation:

x−13 + y−

13 y ′ = 0

We just solve for y ′:

Example 3

We now have the equation:

x−13 + y−

13 y ′ = 0

We just solve for y ′:

y−13 y ′ = −x−

13

Example 3

We now have the equation:

x−13 + y−

13 y ′ = 0

We just solve for y ′:

y−13 y ′ = −x−

13

y ′ = −x−13

y−13

Example 3

We now have the equation:

x−13 + y−

13 y ′ = 0

We just solve for y ′:

y−13 y ′ = −x−

13

y ′ = −x−13

y−13

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