Given f(x)=x² - 6x and g(x)=3x-8, find (g of f)(-1)?

f(x)=x² - 6x
g(x)=3x-8
(g of f)(-1) = g(f(-1)
f(-1) = (-1)^2 - 6(-1) = 1 + 6 = 7
g(7) = 3(7) - 8 = 13

f(x) = x^2 - 6x
g(x) = 3x - 8

g[f(-1)]
= g[(-1)^2 - 6(-1)]
= g[1 + 6]
= g[7]

g(x) = 3x - 8
g(7) = 3(7) - 8
g(7) = 21 - 8
g(7) = 13

( g o f ) ( x ) = g ( x ² - 6 x ) = 3 x ² - 18 x - 8
( g o f ) (- 1) = 3 + 18 - 8
( g o f ) (- 1) = 13

(g of f)(-1) = g(f(-1))
This calls for substituting -1 into the function f(x) first
f(-1) = 1 +6 = 7
Now g(7) = 21 -8 = 13