Answer: Choice A) [tex]9x^2+15x-6[/tex]
=================================================
Work Shown:
[tex]f(x) = x^2+7x\\\\f(x) = (x)^2+7(x)\\\\f(g(x)) = (g(x))^2+7(g(x)) \ \ \text{ ... replace each x with g(x)}\\\\f(g(x)) = (3x-1)^2+7(3x-1) \ \ \text{ ... plug in } g(x) = 3x-1\\\\f(g(x)) = (3x-1)(3x-1)+7(3x-1)\\\\f(g(x)) = 3x(3x-1)-1(3x-1)+7(3x-1)\\\\f(g(x)) = 9x^2-3x-3x+1+21x-7\\\\f(g(x)) = 9x^2+15x-6\\\\(f \circ g)(x) = 9x^2+15x-6\\\\[/tex]
