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)

It’s either a or c as the answer.