Question

in 1A-5b the answer to the answer is that we restrict the domain of the function to x is less than or equal to -1 where as it seems to me that it should be greater than -1

Answer 1

you're right The square root of (x+1) is not defined for values < -1.
plug in -2 for instance: you would get the square root of -2+1 = square root of -1. This does not have a real solution...