My brain is mush - so help me do my homework.

[JimJ 5,000+ posts]

Alright...after being on campus for 12 hours, I'm starting to lose my sanity...I know the basic principle behind what I'm doing, I just can't get the numbers to work out well.

I'm trying to show that Q = 9,000 + 450e^-0.022t is the solution to the differential equation Q' = 198 - 0.022Q, with an initial value of Q(0) being 9,450. This is the decrease of a population of fish or something.

I know that you have to get the diff. equation into the form Q = Ce^kT, where k = the rate of decrease, -0.022 and the T is the time in months. Plug the initial value in for the population, set the time to zero and solve for C. That's alright.

Where I'm lost is where the 198 goes...I'm teh **** at algebra, so I'm probably forgetting where to put it...can someone work this out?

Math > me.

Click to read more...

 

[ToyTundra 10+ year member]

dont you find Q':

Q'=450*-0.022e^-.022t

then plug that and Q into Q' = 198 - 0.022Q and both sides are equal so it is a solution

 

[alove_85 10+ year member]

//content.invisioncic.com/y282845/emoticons/eek.gif.771b7a90cf45cabdc554ff1121c21c4a.gif//content.invisioncic.com/y282845/emoticons/waycrazy.gif.f4a380c3f94043939fd369defd9e6be2.gif//content.invisioncic.com/y282845/emoticons/wow.gif.23d729408e9177caa2a0ed6a2ba6588e.gif i have no ****ing clue what any of that is, I can't even multiply fractions lol

 

[chinny 5,000+ posts]

wtf lol...

 

[JimJ 5,000+ posts]

dont you find Q':
Q'=450*-0.022e^-.022t

then plug that and Q into Q' = 198 - 0.022Q and both sides are equal so it is a solution

d00d!

That makes sense...I remember that from a lecture.

As for the other two guys - this is what you have to look forward to if you take a calc class in college //content.invisioncic.com/y282845/emoticons/yumyum.gif.0556df42231b304b9c995aefd13928a8.gif//content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif

 

[creater 10+ year member]

now im afraid of college work

 

[80INCHES 5,000+ posts]

hey jack i think the Q=9,000 thru u off...it kind of thru me off but when really scratched my brain and thought about it..for all side to be equal the Q has to be equal to 198- 0.022Q

80

i remember in math alot of these kinds of problems deal with substitutions

 

[skierxx5556 10+ year member]

d00d!
That makes sense...I remember that from a lecture.

As for the other two guys - this is what you have to look forward to if you take a calc class in college //content.invisioncic.com/y282845/emoticons/yumyum.gif.0556df42231b304b9c995aefd13928a8.gif//content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif

Problems like that one are the reason why I had to withdraw from my calc class...

 

[alove_85 10+ year member]

d00d!
That makes sense...I remember that from a lecture.

As for the other two guys - this is what you have to look forward to if you take a calc class in college //content.invisioncic.com/y282845/emoticons/yumyum.gif.0556df42231b304b9c995aefd13928a8.gif//content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif

i graduate in may with an associates in wireless communications/ electronics technician, so yay! no calc for me //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[80INCHES 5,000+ posts]

i learned similar problems like that in high school.......i went to college for socialogy

go figure...i should have went to get a electronic engineer degree

80

hmm i'm only 25 so i can still do it

 

[ballstothewall 10+ year member]

Yeah, i get alot of this to look forward to, I get to take calck 1-3, yippie...//content.invisioncic.com/y282845/emoticons/crying.gif.ec0ebefe590df0251476573bc49e46d8.gif (currently in construction science, gonna change to mech. engineering)

 

[Untouchable11 10+ year member]

yes, calculus sucks, and Jack Frost, we just got through a chapter of doing all that stuff.. definately not fun...

Biomedical Engineering > Me

 

[Heresy 10+ year member]

I am trying to do the problem with Laplace Transforms just for fun, and I almost have it worked out except the constants aren't coming out right. High level calculus isn't hard; it just makes you screw up basic math more. //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

 

[ToyTundra 10+ year member]

Yeah, i get alot of this to look forward to, I get to take calck 1-3, yippie...//content.invisioncic.com/y282845/emoticons/crying.gif.ec0ebefe590df0251476573bc49e46d8.gif (currently in construction science, gonna change to mech. engineering)

I'm an ME junior. Have fun. Once you get past Diff Eq it will be used in every class you take //content.invisioncic.com/y282845/emoticons/uhoh.gif.c07307dd22ee7e63e22fc8e9c614d1fd.gif

 

[JAZN 5,000+ posts]

I ). Too bad this problem was already solved by the time I got here. [/propagation of stereotype that asians are math nerds]