Qa help!!

[sweetkitty89]

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f(x) = X^3 + 2X and g is the inverse of f, then g'(3) is??

the explanation to the problem said that it's tough to see that f(1) =3.

and ya.. I don't understand how this thing works.Please explain in super

detail.. step by step if you know this thing..

don't post any comments unless you tried and got g'(3) = 1/15 as an answer.

and please.. if you just wanna make fun of someone who's not smarter than you are, do so in "what are my chances to get in to pharm school" section.
let's not be mean to ppl who suck at math.. their lives already suck..😡

 

[trljjl03]

Inverses can be found by switching y and x and then solving again for y.

Like this -
f(x)= y = 2x -----> x = 2y ---> y = x/2 = invf(x) = g(x)

Because of this f(g(x) = x every time ---> f(g(x) = 2(x/2) = x

Then you take the derivative of both sides of the above equations
f ' [g(x)] *g ' (x) = 1
Move things around and you get g '(x) = 1/[f '[g(x)]]

You need g'(3) so
g '(3) = 1/[f '[g(3)]]

You need g(3) so you need to find an x that makes f(x) = 3
x^3 + 2x = 3
You can see that x = 1 because 1+2=3
Now that you know g(3) = 1 you can put it into the equation.

g '(3) = 1/[f '(1)]
f '(1) = 3(1)^2 +2 = 5
g '(3) = 1/5

Your answer key might be wrong if it says that g'(3) is supposed to be 1/15. I checked this a couple times and I'm pretty sure it's supposed to be 1/5.

 

[sweetkitty89]

Inverses can be found by switching y and x and then solving again for y.

Like this -
f(x)= y = 2x -----> x = 2y ---> y = x/2 = invf(x) = g(x)

Because of this f(g(x) = x every time ---> f(g(x) = 2(x/2) = x

Then you take the derivative of both sides of the above equations
f ' [g(x)] *g ' (x) = 1
Move things around and you get g '(x) = 1/[f '[g(x)]]

You need g'(3) so
g '(3) = 1/[f '[g(3)]]

You need g(3) so you need to find an x that makes f(x) = 3
x^3 + 2x = 3
You can see that x = 1 because 1+2=3
Now that you know g(3) = 1 you can put it into the equation.

g '(3) = 1/[f '(1)]
f '(1) = 3(1)^2 +2 = 5
g '(3) = 1/5

Your answer key might be wrong if it says that g'(3) is supposed to be 1/15. I checked this a couple times and I'm pretty sure it's supposed to be 1/5.

you are very awesome.
Thanks bunch!!👍

 

[BBB PhD]

f(x) = X^3 + 2X and g is the inverse of f, then g'(3) is??

the explanation to the problem said that it's tough to see that f(1) =3.

and ya.. I don't understand how this thing works.Please explain in super

detail.. step by step if you know this thing..

don't post any comments unless you tried and got g'(3) = 1/15 as an answer.

and please.. if you just wanna make fun of someone who's not smarter than you are, do so in "what are my chances to get in to pharm school" section.
let's not be mean to ppl who suck at math.. their lives already suck..😡

I can fix this for you,... right then.... lets get to it
Trust me, ok...I've a PhD in Math and have tagught at 3 universities. So I wouldn't give a reply unless i was 100% sure it is right. Now then,.
1. This is like precalc to me...i didnt realize you all needed that ... nevertheless,... precalc's easier than intermediate algebra and trig so what's the harm.

RE:f(x) = X^3 + 2X and g is the inverse of f, then g'(3) is??

the explanation to the problem said that it's tough to see that f(1) =3.

and ya.. I don't understand how this thing works.Please explain in super

detail.. step by step if you know this thing..



1. OK, why is f(x) with x=1 3?. Just substitute 1 into the function 'f' for the variable 'x'. This results is: f(x) = x^3 + 2(x) |x==1 ----> f(1) =(1)^3 +2*(1) = 1 + 2 =3.

Now, let me do the next on paper and see if the old text made an error (trust me they do a lot )... just a moment, ok?

Alright, I believe the problem ( not the solution is misprinted) ... As written this is not the type problem you should be having in any of your study aides.
I will solve it using answer = 1/15.
I think the problem should be something like f=x^3+2x+3 or something so... I will get to bottom of this. In meantime,...you forget it and move on, ok?
LOL

Now it's in my lap....🙂

 

[sweetkitty89]

I can fix this for you,... right then.... lets get to it
Trust me, ok...I've a PhD in Math and have tagught at 3 universities. So I wouldn't give a reply unless i was 100% sure it is right. Now then,.
1. This is like precalc to me...i didnt realize you all needed that ... nevertheless,... precalc's easier than intermediate algebra and trig so what's the harm.

RE:f(x) = X^3 + 2X and g is the inverse of f, then g'(3) is??

the explanation to the problem said that it's tough to see that f(1) =3.

and ya.. I don't understand how this thing works.Please explain in super

detail.. step by step if you know this thing..



1. OK, why is f(x) with x=1 3?. Just substitute 1 into the function 'f' for the variable 'x'. This results is: f(x) = x^3 + 2(x) |x==1 ----> f(1) =(1)^3 +2*(1) = 1 + 2 =3.

Now, let me do the next on paper and see if the old text made an error (trust me they do a lot )... just a moment, ok?

Alright, I believe the problem ( not the solution is misprinted) ... As written this is not the type problem you should be having in any of your study aides.
I will solve it using answer = 1/15.
I think the problem should be something like f=x^3+2x+3 or something so... I will get to bottom of this. In meantime,...you forget it and move on, ok?
LOL

Now it's in my lap....🙂

man.. i just hope you are doing find with your degree...+ your personality..
i understand that you have nowhere else to let out your anger. Usually people hangout with their friends if they have time to write all these unnecessary junk. If you ever happened to become a pharmacist, please, don't be so twisted like this.

 

[chemguy79]

man.. i just hope you are doing find with your degree...+ your personality..
i understand that you have nowhere else to let out your anger. Usually people hangout with their friends if they have time to write all these unnecessary junk. If you ever happened to become a pharmacist, please, don't be so twisted like this.

What a snotty post. I didn't realize that you are a forum diety who can state what she permits in her thread.

Furthermore, you are violating the TOS by asking for homework answers on SDN.

 

[owlegrad]

man.. i just hope you are doing find with your degree...+ your personality..
i understand that you have nowhere else to let out your anger. Usually people hangout with their friends if they have time to write all these unnecessary junk. If you ever happened to become a pharmacist, please, don't be so twisted like this.

I thought he was trying to help you? Am I missing something?

 

[owlegrad]

What a snotty post. I didn't realize that you are a forum diety who can state what she permits in her thread.

You crack me up.

 

[chemguy79]

you crack me up.

 

[owlegrad]

Did you mean this by any chance? 😀

 

[chemguy79]

Did you mean this by any chance? 😀

I was going back and forth between "cheeky" and "big grin". I'm stuffing my face with a poppy seed bagel for lunch, so I was wary of committing TOOTHFAIL. 😱

 

[owlegrad]

Good choice. 👍