Sorry, I made a mistake:
The field equation for empty space with cosmical constant ist
R_{ij} - \dfrac{1}{2} R g_{ij} + \Lambda g_{ij} = 0
And the exercise said, that R_{ij} + \Lambda g_{ij} = 0
So this means, that \dfrac{1}{2} R g_{ij} is 0
How this becomes zo zero?
Is my...