Problems with the diff function

Hello everyone. I am trying to calculate the following exact differential equation:

(2y-2xy^3 + 4x +6)dx + (2x -3x^2y^2 -1) = 0

First, I divide the equation into two parts, M and N. Then, I try to calculate their derivatives to see if both coincide in order to see if it is an exact equation. I do this with the diff function and this is where the problem arises. When I run the following code:

syms x y
M = '2 * y - 2 * x * y^3 + 4* x + 6';
N = '2*x - 3*x^2*y^2 -1 '

cond = diff(M,y) - diff(N,x)

I get the following error: Difference order N must be a positive integer scalar

Does anyone know how to solve this problem? Thank you very much.

Answer 1

[Stephen23]

syms x y
M = 2 * y - 2 * x * y^3 + 4* x + 6

M = 

N = 2*x - 3*x^2*y^2 -1

N = 

cond = diff(M,y) - diff(N,x)

cond = 

0

Note:

diff(M,y)

ans = 

diff(N,x)

ans = 

Answer 2

[Torsten]

syms x y
M = 2*y - 2*x*y^3 + 4*x + 6;
N = 2*x - 3*x^2*y^2 - 1 ;
cond = diff(M,y) - diff(N,x)