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  • - [Voiceover] Let F be a function such that

  • F of negative one is three.

  • And F prime of negative one is equal to five.

  • Let G be the function G of X

  • is equal to one over X.

  • Let capital F be a function defined as

  • the product of those other two functions.

  • What is capital F prime of negative one?

  • Well, we can just apply the product rule here,

  • let me just rewrite let me just

  • essentially state the product rule.

  • Capital F prime of X

  • is going to be equal to

  • since capital F of X is the product

  • of these two functions,

  • when we apply the product rule this is gonna be

  • F prime of X

  • times G of X

  • plus plus

  • F of X

  • times G prime of X.

  • And so if we want to evaluate this

  • at F of negative one

  • capital F prime

  • at negative one is equal to

  • F prime of negative one

  • times G of negative one

  • plus function F evaluated at negative one

  • times the derivative of G

  • evaluated at negative one.

  • And let's see if we can figure these things out.

  • So do they tell us this anywhere?

  • Can we figure this out?

  • F prime of negative one.

  • Well they tell us right over here

  • F prime of negative one

  • is equal to five.

  • So this is equal to five.

  • Now, let's actually stick with F.

  • What is F of negative one?

  • Well, they tell that to us

  • right over here.

  • F of negative one is equal to three.

  • So F of negative one is equal to three.

  • Now G of negative one

  • and G prime of negative one

  • they don't give it to us explicitly here

  • but we can figure it out.

  • We can, we know that if G of X

  • is equal to this

  • G of negative one is equal

  • to one over negative one

  • which is equal to negative one.

  • So this is equal to

  • negative one.

  • And then last but not least

  • if we want to find G prime of negative one

  • we just have to take the derivative of this.

  • So G prime of X.

  • Actually just let me rewrite G of X.

  • G of X

  • one over X is just the same thing

  • as X to the negative one.

  • So we're gonna use a power rule

  • to figure out G prime of X

  • is equal to bring that exponent

  • out front, negative one times X

  • to the and then decrement the exponent

  • negative two power.

  • So, G prime of

  • negative one

  • of negative one is equal to

  • negative one times

  • negative one to the

  • negative two power.

  • And that's just the same thing as

  • negative one over negative one squared.

  • This is one.

  • So this is just all going to evaluate

  • to negative one.

  • So this is

  • negative one.

  • And so we have

  • five times negative one

  • which is negative five.

  • Plus three times negative one

  • which is negative three.

  • Which is equal to

  • negative eight.

  • So F prime of negative one

  • is equal to negative eight.

- [Voiceover] Let F be a function such that

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A2 初級

Worked example: Product rule with mixed implicit & explicit | AP Calculus AB | Khan Academy

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    yukang920108 に公開 2022 年 07 月 12 日
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