# y=y+2 Seems Simple, but i can't match the answer up to it.

• March 28th 2012, 12:06 PM
Deo3560
y=y+2 Seems Simple, but i can't match the answer up to it.
The equation is:
dy/dx=y+2

The answer is y=Cex-2

Can anyone explain this?
• March 28th 2012, 12:42 PM
Ridley
Re: y=y+2 Seems Simple, but i can't match the answer up to it.
The answer looks correct. You can easily check if it's correct yourself by finding the derivative and plugging it back into the equation.
• March 29th 2012, 09:35 AM
thelostchild
Re: y=y+2 Seems Simple, but i can't match the answer up to it.
If you also want to see why write
the equation is seperable and can be written as
$\int \frac{dy}{y+2} = \int dx$

so
$\ln (y+2) = x + c$

then taxing the exp of both sides and writing the arbitrary constant as C = ln c gives the solution as you have it
• March 30th 2012, 03:38 PM
Creebe
Re: y`=y+2 Seems Simple, but i can't match the answer up to it.
Or you can check the answer by taking the derivative of it:

$\frac{d}{dx} y(x) = Ce^x$

So you put this back into the differential equation:

$Ce^x = [Ce^x - 2] + 2$

It turns out to be true.