How do you make separable equations for the following equations:

dy/dx = (b/y)*sqrt(1-(x^2/a^2)) - k*y

dy/dx = (m*x+b)/y - k*y

dy/dt = b*sqrt(1-(t^2/a^2)) - k*y^2

dy/dt = m*t + b - k*y^2

the variables y, x, and t are the variables that are not constants, dy/dx or dy/dt denotes derivatives, and sqrt() means that it is the square root of what is in the parentheses.

Any help will be appreciated very much