Trouble using the chain rule product rule and quotient rule

In summary, the conversation is about the correct use of the chain rule, product rule, and quotient rule in finding derivatives. The person is struggling with using these rules together and asks for help. They receive guidance on factoring and simplifying their answer, and ultimately, they are able to find the correct solution with the help of the expert.
  • #1
dcgirl16
27
0
im having a lot of trouble using the chain rule product rule and quotient rule..i can do them fine seperatly but when they're put together i can't get them like if you have (x^2-1)^4 (2-3x) i would start with
4(x^2-1)^3(2x)(2-3x)+(x^2-1)^4(-3)
have i done something wrong here because i never get the right answer with these ones i don't know if i messed up here or later on
 
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  • #2
You evaluation of the derivative is correct.
 
  • #3
ok so the next thing i would do would be to factor out the (x^2-1)to get
(8x)(x^2-1)^3(2-3x)+(x^2-1)(-3)
is this still right?
 
  • #4
i should have a 1 in there before the plus sign too
 
  • #5
No. you've not factored out the (x^2-1), since you have (x^2-1)^3 in the first term. You're second term is incorrect since it should still be (x^2-1)^4. If you take out (x^2-1)^3 from both terms, and put it outside a bracket at the front, what do the remaining terms in the bracket look like?
 
  • #6
would it be
((x^2-1)^3)(1)(8X)(2-3X)+(x^2-1)(-3) ?
 
  • #7
You're missing a bracket.. write it like this, omitting the unnecessary ones:
(x^2-1)^3(8x(2-3x)-3(x^2-1)).

Now, can you simplify this?
 
  • #8
my first thought would be to multiple the 8x and -3 through their brackets then combine like terms?
 
  • #9
dcgirl16 said:
my first thought would be to multiple the 8x and -3 through their brackets then combine like terms?

Good idea. Give it a go and see what you come up with.
 
  • #10
ok that workedi got the right answer thanks for your help
 
  • #11
You're very welcome!
 

FAQ: Trouble using the chain rule product rule and quotient rule

1. What are the basic rules for solving problems using the chain rule, product rule, and quotient rule in calculus?

The chain rule is used to find the derivative of a function within another function. The product rule is used to find the derivative of a product of two functions. The quotient rule is used to find the derivative of a quotient of two functions.

2. How do I know when to use the chain rule, product rule, or quotient rule in a problem?

The chain rule is typically used when you have a function within another function, such as f(g(x)). The product rule is used when you have two functions being multiplied together, f(x)g(x). The quotient rule is used when you have two functions being divided, f(x)/g(x).

3. What are some common mistakes to avoid when using the chain rule, product rule, and quotient rule?

Some common mistakes include forgetting to apply the chain rule, mixing up the order of terms in the product rule, and incorrectly applying the quotient rule (remember to use the negative exponent for the bottom function).

4. How do I simplify my answer when using the chain rule, product rule, and quotient rule?

To simplify your answer, you can use algebraic manipulations such as factoring, combining like terms, and simplifying fractions. You can also use common derivative rules, such as the power rule, to simplify your answer.

5. Are there any tips or tricks for remembering how to use the chain rule, product rule, and quotient rule?

One tip is to remember the phrase "low d-high minus high d-low over low squared" for the quotient rule. Another tip is to practice, practice, practice! The more you use these rules, the easier they will become to remember and apply.

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