getting burnt out

[ChopstickHero]

calc is so boring. i remember sitting thru class staring out the window. the problems were so dumb and unapplicable to real life. i'm just glad i got 89% and didn't have to retake it. university calc is a whole other story...

 

[geomatics_tech]

i used my hp 49g calculator for all my calculus, it does step by step derivatives and integration.... .....just punch in the equation and it derives/integrates step by step for full marks on the test.

good luck (cause im not even going to look at the question)

 

[Lord_Zath]

Dexter750: so V=x^2h
Dexter750: consequently 20 = x^2h
Dexter750: to get the h out of the cost function, solve the volume one for h
Dexter750: 20/x^2 = h
Dexter750: plug that back into the cost one, right, and you've got all x's

12(x(20/x^2) + 5(x^2) = Cost

ok I see now no top. crackrox in a box w/no top. haha. anyways.

is it v = (x^2)*h or is it v= x^(2*h)?

If it's the former, then you can do the operation you did. If it's the latter, it's time to bust out the log.

 

[Dexter]

v = (x^2)*h.

i spent like two hours on that damn problem for the homework. the closest thing i could get to an aswer was like X < 4.68566 or some s***. whatever, i just made stuff up and turned it in. *shrugs*.

afa the test went, i think i only got one wrong...amazing...
luckily i have a TI-89 which can do calc (derivs and integration s****)...we're not supposed to be able to use them with tests (only TI-83), but the teacher never checks..so...**** yeah for getting by...

 

[1sty]

Cal was fun, got a A
Calc II was better, got an A+

 

[Lord_Zath]

haha awesome.

 

[goku4658]

i did well in calc in both high school and college...i have no idea how...i assume all mathematical knowledge i possessed went *up in smoke*

 

[Dexter]

Cal was fun, got a A
Calc II was better, got an A+

I took calc before, got a C. Im retaking it now, hoping for an A...
i took calc II before also, and dropped it before midterms. bleh.

 

[sanblaster]

I took calc in college 3 times. Dropped it twice; third times a charm. Calc is why I chose architecture over engineering. So did some of my buddies. And we were checked for TI-89's during tests.

 

[goku4658]

ti-89's are the ish! u guys ever play drug wars on your calculators?

 

[sanblaster]

ti-89's are the ish! u guys ever play drug wars on your calculators?

s*** the only war I was ever involved with my TI-83 calculator was algebra and trigonometry. Exciting huh? I lost quite a bit.

 

[jurgs01]

i have to calculate the cost for this box, alright

its got a square base
Dexter750: (x by x)
Dexter750: and height h
Dexter750: material for the sides costs 3 dollars sq/ft
Dexter750: and for the base is 5 dollars sqft
Dexter750: also, there is no top
Dexter750: so its cost of base + cost of 4 sides, right?
Dexter750: 5(x^2)+4(3(xh))
Dexter750: makes sense, right
Dexter750: volume is fixed at 20 cubic feet
Dexter750: so V=x^2h
Dexter750: consequently 20 = x^2h
Dexter750: to get the h out of the cost function, solve the volume one for h
Dexter750: 20/x^2 = h
Dexter750: plug that back into the cost one, right, and you've got all x's

12(x(20/x^2) + 5(x^2) = Cost of the Crackrock storage box
^ did i get that correctly?

The company that mfgs these containers has determined it can afford a cost of at most 160 per container. What dimensions for the container produce a cost of at most 160. Explain the procedure you used to solve this problem.

solving that b**** of a cost equation for 160 doesnt work...because no x will ever make it equal exactly 160 (i been playing with an excel sheet i made and my graphing calculator...it wont even solve for x.....so what the fux to me)...

cancel the x in the numerator and denominator and you get 5x^2 + 240/x = y (y = total cost) Take the derivative of y with respect to x and you get dy/dx = 10x - 240/x^2. If you set dy/dx = 0 and solve for x you get your points of inflection which tell you the x values that have the minimum and maximum values in your original y function. The question doesn't ask for you to get a cost of exactly 160 it says AT MOST.

 

[goku4658]

^^like whoa

 

[Dexter]

damnit jurgs, why didnt i think of that...blah, i was so stupid last night, all day doing problems and then trying to do that damn homework sheet...oh well, hopefully i still get a decent grade. thanks for explaining it

 

[jurgs01]

I edited the post for a small error The derivative of 1/x is -1/x^2 not ln(x). It's been a while since calc for me(crazy)

 

[sanblaster]

I edited the post for a small error The derivative of 1/x is -1/x^2 not ln(x). It's been a while since calc for me(crazy)

You still DA man jurgs. (boom01)

 

[Dexter]

I edited the post for a small error The derivative of 1/x is -1/x^2 not ln(x). It's been a while since calc for me(crazy)

okay, yeah, i actually did do that, to solve for the critical numbers (where f'(x) = 0)

 

[jurgs01]

okay, yeah, i actually did do that, to solve for the critical numbers (where f'(x) = 0)

Yes. So when you solved for those x you have the critical numbers. You plug them into the original y equation to see whether they are minimums or maximums (you want mininimum), then plug that x into the equation with h to get your h. You did it right if you did that.

 

[siberiankiss]

i just finished cal 3 last semester. got over a 100 in both cal 1 and 2, but an A- in cal 3. we were allowed any calculator in cal 1, but after that we weren't allowed any calculators at all... not even little 4 function ones. major suckage.

 

[Dexter]

Yes. So when you solved for those x you have the critical numbers. You plug them into the original y equation to see whether they are minimums or maximums (you want mininimum), then plug that x into the equation with h to get your h. You did it right if you did that.

lol, i dont even remember. (see thread title )