# solve differential equations

• Jul 20th 2013, 09:47 AM
muddywaters
solve differential equations
for the first one, "However when k=0, y=1. This also satisfies (1)" what to they mean by that? there is no 'k' in (1) is dy/dx = 0 because k=0? why?

for the second one, 'however when y=1,-1, dy/dx=0' how to get dy/dx=0?
• Jul 20th 2013, 07:07 PM
chiro
Re: solve differential equations
Hey muddywaters.

Hint: When y = c (i.e. a constant) then what is the derivative?
• Jul 21st 2013, 12:08 AM
muddywaters
Re: solve differential equations
Quote:

Originally Posted by chiro
Hey muddywaters.

Hint: When y = c (i.e. a constant) then what is the derivative?

oh thanks. for the second one i got stuck because i thought should substitute y=1,-1 into $x=-\sqrt{1-y^2}+C$ that would give me x = c which cannot give dy/dx = 0. but actually y=1,-1 is itself the solution.