6.4 Implicit Differentiation

MATH 151 SI Name 6.4-­β€6.5 6.4 Implicit Differentiation How to find dy/dx implicitly? 1. Take the derivative of the function: Example 𝑦 ln π‘₯ + 4π‘₯ = 13𝑦 Derivative aaa All normal rules apply (power, product, !
quotient, exponential, log, chain) β€’
Did you take the derivative of y? Multiply by dy/dx o
Did you take the derivative of x? β€’
Leave this as is (or multiply by o
dx/dx=1) 2. Move all terms with a dy/dx in them to one side of the equation and all terms without dy/dx to the other side β€’
You may need to expand or get rid of your fractions 3. Factor out dy/dx and solve for dy/dx 2𝑦 ln π‘₯ βˆ™
+
!!
!
+ 4 = 13 βˆ™
!"
!"
𝑑𝑦 𝑦 !
𝑑𝑦
+
+ 4 = 13 βˆ™ 𝑑π‘₯
π‘₯
𝑑π‘₯
𝑦!
𝑑𝑦
𝑑𝑦
+ 4 = 13 βˆ™
βˆ’ 2𝑦 ln π‘₯ βˆ™ π‘₯
𝑑π‘₯
𝑑π‘₯
by dividing by what is left !"
You took the derivative of y so multiply by dy/dx 2𝑦 ln π‘₯ βˆ™
!"
𝑦!
𝑑𝑦
+4=
(13 βˆ’ 2𝑦 ln π‘₯) π‘₯
𝑑π‘₯
𝑑𝑦
𝑦!
4
=
+
𝑑π‘₯ π‘₯ 13 βˆ’ 2𝑦 ln π‘₯
13 βˆ’ 2𝑦 ln π‘₯