New Reply

Help With Solving This Differential Equation

 
Share Thread Thread Tools
Feb27-12, 10:51 PM   #1
 

Help With Solving This Differential Equation


1. The problem statement, all variables and given/known data

1. The slope of a function at any point (x,y) is 〖2e〗^x/(e^x+2) . The point (0,2ln3) is on the graph of f.

(A) Write an equation of the tangent line to the graph of f at x=0.
(B) Use the tangent line in part A to approximate f(0.3) to the nearest thousandth.
(C) Solve the differential equation dy/(dx )=(2e^x)/(e^x+2) with the initial condition f(0)=2ln3.
(D) Use the solution in part C to find f(0.3) to the nearest thousandth.



2. Relevant equations



3. The attempt at a solution


(A)

dy/(dx )=(2e^x)/(e^x+2)

At x=0, dy/dx=(2e^0)/(e^0+2)=2/3

Equation of tangent line at x=0: y-2ln3=2/3 (x-0)

y-2ln3=2/3 x or y=2/3 x+2ln3

(B)

f(0.3)≈2/3 (0.3)+2ln3≈2.39722≈2.397

(C)

dy/dx=〖2e〗^x/(e^x+2) → dy=(2e^x)/(e^x+2) → ∫dy= ∫〖(2e^x)/(e^x+2) dx〗

Let u=e^x+2, du=e^x dx
2du=2e^x

Here is where I run into problems. Can anybody help me with the rest? Any help would be greatly appreciated.
PhysOrg.com
PhysOrg
science news on PhysOrg.com

>> Galaxies fed by funnels of fuel
>> The better to see you with: Scientists build record-setting metamaterial flat lens
>> Google eyes emerging markets networks
Feb27-12, 11:25 PM   #2
 
bump. please, i'm desperate for help.
Feb27-12, 11:28 PM   #3
 
Mentor
Quote by helpmeimdumb View Post
1. The problem statement, all variables and given/known data

1. The slope of a function at any point (x,y) is 〖2e〗^x/(e^x+2) . The point (0,2ln3) is on the graph of f.

(A) Write an equation of the tangent line to the graph of f at x=0.
(B) Use the tangent line in part A to approximate f(0.3) to the nearest thousandth.
(C) Solve the differential equation dy/(dx )=(2e^x)/(e^x+2) with the initial condition f(0)=2ln3.
(D) Use the solution in part C to find f(0.3) to the nearest thousandth.

2. Relevant equations

3. The attempt at a solution

(A)

dy/(dx )=(2e^x)/(e^x+2)

At x=0, dy/dx=(2e^0)/(e^0+2)=2/3

Equation of tangent line at x=0: y-2ln3=2/3 (x-0)

y-2ln3=2/3 x or y=2/3 x+2ln3

(B)

f(0.3)≈2/3 (0.3)+2ln3≈2.39722≈2.397

(C)

dy/dx=〖2e〗^x/(e^x+2) → dy=(2e^x)/(e^x+2) → ∫dy= ∫〖(2e^x)/(e^x+2) dx〗

Let u=e^x+2, du=e^x dx
2du=2e^x

Here is where I run into problems. Can anybody help me with the rest? Any help would be greatly appreciated.
Rewrite your integral in terms of the variable, u .
New Reply

Tags
ap calculus ab, assistant needed, calculus, integration, u substitution
Thread Tools


Similar Threads for: Help With Solving This Differential Equation
Thread Forum Replies
Solving a Differential Equation Calculus & Beyond Homework 7
Solving a partial differential equation (Helmholtz equation) Differential Equations 7
Help solving a Cauchy-Euler Equation (Differential equation help) Calculus & Beyond Homework 2
Need help solving a differential equation Calculus & Beyond Homework 1
solving this differential equation Classical Physics 7