Question

Differential equation
Find the differential equation for the family of curve cy + lnx = 0

Answer 1

? take the derivative of that?

Answer 2

I think taking the derivative is one of the steps. But I don't really know how to do it (I mean solving the whole question)

Answer 3

you cant solve that

Answer 4

3 variables in 1 equation

Answer 5

I meant I can't find the differential equation.

Answer 6

paste exactly what the book says to do

Answer 7

This is the exact question - no missing words.

Answer 8

i dif eq has the form dy/dx =.... or something like that, but you must know with what it is respect to

Answer 9

you must know what variable to take the derviative in respect to.

Answer 10

It didn't mention in the book, but I think it is w.r.t. x

Answer 11

did it say family curve or family of curves?

Answer 12

Ouch! family of curve. Sorry for that - one word missing

Answer 13

so y = -lnx/c

Answer 14

so y = -1/c * lnx
dy/dx = -1/c * d(lnx)/dy

Answer 15

can you do that?

Answer 16

For the right side, what should it be -1/c * d(lnx)/dy ?

Answer 17

Aren't we diff. w.r.t x?

Answer 18

dx/dy is in respect to y

Answer 19

Yes. But why did you diff. the left sides with respect to x while diff the right side with respect to y?

Answer 20

o sorry that should be dx

Answer 21

So, \(\frac{dy}{dx} = -\frac{1}{c} \times \frac{d(lnx)}{dx}\)
\(\frac{dy}{dx} = -\frac{1}{cx}\)
And then?