using (f ○ g)(x) = f(g(x))
substitute x = [tex]\frac{7}{x}[/tex] into f(x)
f( [tex]\frac{7}{x}[/tex]) = 4 / ([tex]\frac{7}{x}[/tex] - 3 ) × [tex]\frac{x}{x}[/tex]
= [tex]\frac{4x}{7-3x}[/tex]
The denominator of f(g(x)) cannot be zero as this would make f(g(x)) undefined. Equating the denominator to zero and solving gives the value that x cannot be
solve 7 - 3x = 0 ⇒ x = [tex]\frac{7}{3}[/tex]
domain : x ∈ ( - ∞, [tex]\frac{7}{3}[/tex]) ∪ ( [tex]\frac{7}{3}[/tex], + ∞ )
