### differential equation problems.

I am trying to get the differential equation examples to work:

x = var('x')
y = function('y',x)
desolve(diff(y,x) + y - 1, y)

or

t = var('t')
x = function('x',t)
DE = diff(x, t) + x - 1
desolve(DE, [x,t])

Both return errors. What am I doing wrong?