Hi. Got 2 more questions on index placements. 1 - I found the following on an exam paper and it seems wrong to me. It concerns a weak perturbation to the Minkowski metric gik = ηik + hik. It then states that to first order in hik the contravariant metric tensor is gik = ηik - ηinηkmhnk. This seems wrong to me as the RHS has a free m index but the LHS does not. I think 2nd term on the RHS should be -ηaiηbkhab which I think is equal to -hik. Am I right ? 2 - In some notes I found nuvTuv = Tuv. This doesn't seem right either but i'm not sure exactly what it should be ? If I contract the u I get Tvv but if I contract the v first I get Tuu. Are these different ? Do they both equal scalar T ?