Given the following
f(x) = x-5
g(x) = x^2-1
(f-g)(x) = f(x) - g(x)
Substitute the given function into the expression
(f-g)(x) = x-5 - (x² - 1)
(f-g)(x) = x-5-x²+1
(f-g)(x) = -x²+x-4
if x = -1, substitute x = -1 into the resulting function
(f-g)(-1) = -(-1)²+(-1)-4
(f-g)(-1) = -1-1-4
(f-g)(-1) = -6
Hence the value of the expression given is -6