Optimization Example 4

[digitbra]

Number 14 in my textbook!! YES.

[mrmivpushkin]

THX

[NissanConsole123]

You sir have saved my life! Thank You haha

[idiotrun1997]

I didn't know you could do that with Google lol

[RawrDinosawrM]

Don't you need to plug back in the x to the cost equation to completely answer the question of the cheapest COST? resulting in $163.54 ?

[junior1984able]

Yr amazing

[topik627]

Sometimes it's Fun! (Tony Montana voice)

[guaranic]

Had this exact problem on Webassign. The Final answer is: $163.54

[xniquilador]

1.65 is the width for the cheapest container per specs, but it is not the actual cost. =)

[acbanta]

awesome job! This video saved massive confusion and clarified a lot of points I previously couldn't make sense of! THANK YOU

[NickyNeu]

The answer as the question asked was never answered...

[rubberduckypwn]

Hey Sal! Thanks for the awesome vid. But a question real quick:

At @6:10 when writing the derivative. Why do you reverse the sign? Why isnt it just C=40x PLUS 180x^-2 ?

Thx

[sjsawyer]

@rubberduckypwn The exponent comes out front and you lower the power by 1.

e.g. d\dx x^3 = 3x^2 and likewise d\dx x^(-3) = -3x^(-4)

[s200960170]

Inbox (1623)

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[joemae1]

thank you so much!! made so much sense!

[deadneutral]

just went through all the optimization vids thank you

[micchhin]

THANK YOU.

[ArcticSheep]

thanks! :)

[rayray66]

women's health magazine at 8:58 in the mail! lol, thanks for the video

[TheStever496]

Hello Sal. Really like your videos. Thank you. Was wondering about the cost equation in this video though. Why is the cost equation (@ the 5:10 time point) written: C (x) = 10*2Xsquared + 6*2*5Xto the minus1power + 6*2*10Xto the minus 1 power Instead of either C (x) = 10*2Xsquared + 6*2*10Xto the minus 1 power + 6*2*10Xto the minus 1 power Or C (x) = 10*2Xsquared + 6*2*5Xto the minus 2 power + 6*2*5Xto the minus 2 power ? Thank you. Steve.

[kingzman264]

Why did the pretty box go away?

[danired18]

Awesome video! But you never finished the problem. You need to plug 1.65 back into the C(x) equation in order to find out what the actual cost is.

[jonolollmao]

im so shocked! that differentiation and max/min points on a graph are so useful to real life!!

i can imagine some random guy designing a storage box for a product doing all these workings LOL 

[alaazahra]

lol send me your address and I ill mail you a calculator bro !

[coffeevampiress]

Thank you for talking about how you know whether the answer is a max or a min value. That's been a nagging question in the back of my head for a while, how do you know the answer you are getting is really the one they are asking for, but I will try the second derivative on this one... I'm wondering, what would you do if you had to find the cost of the most expensive box?

[GunnergruntC22]

Great tutorial man. Really helped me out.

[bkisme]

Amazing.

I'm gonna kick the crap out of the 2nd part of my calc test tommorow :D

[hitopachy]

Awsome tutorials helped me get through calc

[blackhearts8]

why is this shit soo easy when people explain it?!?!? fuck... but thanks man... very welll done

[fuckooo]

@blackhearts8 lol just imagine how many people have been turned off of maths worldwide because of textbooks.

[marcusjhung]

crystal clear and easy to understand, thanks Sal

[angelsarah7]

its soooo much clearer when you explain it... i kind of understood it before but now i get it without second guessing what im doing.. thank you!

[kickit246]

can u write my final for me tomorrow plz? lol

[Yoshi3003]

He probably forgot that..

since x = 1.65 m

so base cost = 2x^2 = 2(1.65)^2

and etc..

[iluvjiyongx3]

so u just plug x in and add up the base and sides?

[Yoshi3003]

yep, now we know the length, just substitute it in the cost function. That should be the real final answer.

[iluvjiyongx3]

oh, thanks!!

[brco2003]

lol Yahoo Mail - you're great

[khanacademy]

Exponents take precendence over multiplication so 5x^-2 = 5(x^-2) = 5/(x^2), not (5x)^-2

[GoldAK47]

so I'm right??!!

[khanacademy]

no. It is correct as done in the video

[GoldAK47]

Ohhh I get it now!!! :) Makes so much sence. BEDMAS. I'm such an idiot. You're a genius. Keep it up

[GoldAK47]

Huh? I don't get one part.

You reduced 10/2x^2to 5x^-2, which means it is 1/5^2 when it really should be reduced to 5/x^2. Did you make a mistake there?

(am I making sence :P)??