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Mathematics 9 Online
kaylak:

help @shadow calc

kaylak:

need 2

1 attachment
kaylak:

@mhchen

kaylak:

isn't it like 180 degrees of the graph sorta

mhchen:

|dw:1541565888694:dw|

mhchen:

|dw:1541565932427:dw| Here's where the derivatives are 0

mhchen:

|dw:1541565957973:dw| and there's your slope graph

kaylak:

oh ok

kaylak:

up for 4 more problem? 1 is just an explaining something I have to record myself joy lol

kaylak:

kittybasil:

Kayla, Shadow doesn't help with calculus. Try SmokeyBrown or sillybilly123 instead.

kaylak:

@Falconmaster yu said to tag you but I don't know if you do calc

Falconmaster:

i do geometry but i can try

kaylak:

I have to show my work

Falconmaster:

it should show you the work -think emoji here-

kaylak:

not for free

Falconmaster:

hm idk im sorry Brainly?

kaylak:

@mhchen

mhchen:

Okay so problem 5.

mhchen:

Basically find the second derivative of \[\frac{2}{x}+3\sqrt{x}\]

kaylak:

okay

mhchen:

You can re-write that as: \[2x^{-1}+3x^{\frac{1}{2}}\] Are you able to find the first derivative of that?

kaylak:

3/2x^1/2-2/x^2

kaylak:

second derivative is 4/x^3-3/4x^3/2

mhchen:

woah hold on. the first one should be 3/2^(-1/2) - 2/x^2

mhchen:

You see how the exponent is -1/2 instead of 1/2?

kaylak:

you're right

kaylak:

my teacher gave us the answers but basically wants us to show work to get them

kaylak:

so -3/2?

mhchen:

Yeah

kaylak:

but the rest is correct?

mhchen:

4/x^3-3/4x^(-3/2)

kaylak:

okay

kaylak:

then plug in 4?

mhchen:

Yup

mhchen:

I got -1/32

kaylak:

getting there but yes that's the answer lol

kaylak:

I got it lol

mhchen:

onto problem 6. Instantaneous rate of change just means the derivative. Can you find the derivative of f(x)/x^2

kaylak:

-f/y^2?

mhchen:

it should be like this: \[\frac{f'(x)x^2 - f(x)(x^2)'}{(x^2)^2}\] You know the formula for finding the derivative of division stuff right?

kaylak:

oh yeah I do remember that

kaylak:

and then would I plug x in ?

kaylak:

okay so I did something wrong I go 1/3 and need to have 11/27

mhchen:

yah

mhchen:

uh lemme try it myself

kaylak:

I plugged in the appropriate numbers for x f' and f

mhchen:

\[\frac{f'(3)(3)^2-f(3)(2(3))}{(3)^4} = \frac{(5)(9)-(2)(6)}{81}=\frac{45-12}{81}=\frac{33}{81}\]

kaylak:

oh hold on

kaylak:

got it now number 10

kaylak:

one more this one I messed up somewhere

1 attachment
kaylak:

it is supposed to be x-2 not +2

mhchen:

|dw:1541613940118:dw|

mhchen:

oh uh lemme check 8 first then

mhchen:

I completely forgot how to do 8.

kaylak:

lol

kaylak:

I mean if you plugged in what I have it would still work

kaylak:

let's do 10 lol

mhchen:

|dw:1541614275555:dw| This is a secant.

mhchen:

You see how 'a' is the starting point, and 'h' is how far away it goes

kaylak:

oh I see how 8 is correct

kaylak:

yes

mhchen:

So if you bring 'h' to 0, basically it becomes like this: |dw:1541614370964:dw|

mhchen:

That's a tangent line, AND it's the instantaneous slope at 'a'.

kaylak:

so f(a) is a secant?

kaylak:

just trying to write this down so I can record myself and explain lol

mhchen:

f(a) is just a point. Look at my first picture.|dw:1541614550531:dw| That line there is a secant, and it's made by \[\frac{f(a+h)-f(a)}{h}\] Here is the tangent (and instantaneous slope: |dw:1541614608605:dw| As you can see h is gone because this is \[lim_{h->0}\frac{f(a+h)-f(a)}{h}\]

kaylak:

is that h->0 in other words say it is going further away from 0?

kaylak:

in the negative

mhchen:

It's going towards 0.

mhchen:

It was positive before. But now it's getting smaller towards 0.

kaylak:

okay was a little confused for a sec but ty for the help!

mhchen:

Here is a beautiful gif: https://commons.wikimedia.org/wiki/File:Tangent_animation.gif

kittybasil:

btw Symbolab is great for basic step-by-step walkthroughs of most calculus problems

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