Which statement best describes f (x) = - 2sqrt (x-7+1)

A.-6 is in the domain of f (x) but not in the range of f (x)

B.-6 is not the domain of f (x) but is in the range of of f (x)

C.-6 is in the domain of f (x) and in the range of f (x)

D. - 6 is neither in the domain of f (x) nor in the range of f (x)

Plugging - 6 in for x, we get - 2sqrt (-6-7+1) = sqrt (something negative) which is clearly not possible.

Plugging - 6 in for f (x), we get - 6=-2sqrt (x-7+1) and 3=sqrt (x-7+1). Squaring both sides, we get 9=x-7+1 and by adding both sides by 6 we get 15=x, therefore having (15,-6) and proving that - 6 is in the range, but not the domain (B)