The following differential equations appear similar but have very different

eliaskidszs

eliaskidszs

Answered question

2021-12-26

The following differential equations appear similar but have very different solutions:
dydx=x,
dydx=y
Solve both subject to the initial condition y(1)=2

Answer & Explanation

Lindsey Gamble

Lindsey Gamble

Beginner2021-12-27Added 38 answers

Given:  dy  dx =x 
Separation of variables 
 dy =x dx  
Integrate both sides 
 dy =x dx  
Use: xn dx =xn+1n+1and dy =y 
y=x1+11+1+C 
y=x22+C 
y(1)=2 (Given) 
Solve the original equation at x=1 
2=121+C 
2=1+C 
C=1 
The constant is C=1 and place in the equation for the final answer 
y=x22+1 
Given:  dy  dx =y 
Separation of variables 
 dy y= dx  
Integrate both sides 
 dy y= dx  
Use:  dy y=ln|y|and dx =x 
ln|y|=x+C 
y(1)=2 (Given) 
Solve the original equation at x=1 
ln|2|=1+C 
C=ln|2|1 
The constant is C=ln|2|1 and place in the equation for the final answer 
ln|y|=x+ln|2|1 
Simplify: 
ln|y|ln|2|=x1 
Using: ln|yx|=ln|y|ln|x| 
ln|y2|=x1 
Result: y=x22+1andln|y2|=x1

Raymond Foley

Raymond Foley

Beginner2021-12-28Added 39 answers

1) dydx=x
dy=xdx+c, c is int const.
y=x22+c
Now, y(7)=3
y=3whenx=7
3=492+cc=3492=6492=432
y=12x2432=12(x243)
2) dydx=y
dyy=dx+logc,logc is int const.
logey=x+logee
logeylogc=xloge(yc)=x
yc=exy=cex
Since y=3 atx=7
3=ce7c=3e7
y=3e7ex=3ex7
karton

karton

Expert2022-01-10Added 613 answers

dydx=xdy=xdxdy=xdxxndx=xn+1n+1anddy=yy=x1+11+1+Cy=x22+Cy(1)=2 (Given)x=12=121+C2=1+CC=1C=1 and place in the equation for the final answery=x22+1Given: dydx=ydyy=dxdyy=dxdyy=ln|y|anddx=xln|y|=x+Cy(1)=2 (Given)x=1ln|2|=1+CC=ln|2|1C=ln|2|1ln|y|=x+ln|2|1ln|y|ln|2|=x1ln|yx|=ln|y|ln|x|ln|y2|=x1Answer: y=x22+1 and ln|y2|=x1

Do you have a similar question?

Recalculate according to your conditions!

New Questions in Differential Equations

Ask your question.
Get an expert answer.

Let our experts help you. Answer in as fast as 15 minutes.

Didn't find what you were looking for?