Answer:
f(x) = √7x
g(x) = 1/x -8
To find the domain of f º g we must first find f o g(x)
To find f o g(x) wherever you see x in f(x) replace it by g(x)
That's
f o g = √7(1/x-8)
= √7 / √x - 8
To find the domain equate the denominator to zero
That's
√x - 8 = 0
Square both sides
(√x - 8)² = 0²
x - 8 = 0
x = 8
The domain of f o g is x E R except 8
Hope this helps