Answer
(f - g)(3t) = -9$t^{2}$ + 3t + 5
Work Step by Step
The notation (f - g)(3t) can be rewritten as f(3t) - g(3t). Solving by subtracting the functions then evaluating at 3t will yield the same result as evaluating each function and then subtracting.
In this question:
f(x) = x + 3
g(x) = $x^{2}$ - 2
Method 1: Subtract the functions then evaluate
First we want to subtract the two functions. The new function will be called h(x).
h(x) = f(x) - g(x)
h(x) = (x + 3) - ($x^{2}$ - 2)
h(x) = x + 3 - $x^{2}$ + 2
Combine like variables to get:
h(x) = -$x^{2}$ + x + 5
Evaluate at x = 3t:
h(3t) = -$(3t)^{2}$ + 3t + 5 = -9$t^{2}$ + 3t + 5
Method 2: Evaluate the functions and then subtract
First we want to evaluate f(x) at x = 3t:
f(3t) = 3t + 3
Then we want to evaluate g(x) at x = 3t:
g(3t) = $(3t)^{2}$ - 2 = 9$t^{2}$ - 2
Subtract the numbers together:
(f - g)(3t) = 3t + 3 - (9$t^{2}$ - 2) = 3t + 3 - 9$t^{2}$ + 2 = -9$t^{2}$ + 3t + 5
Using both methods (f - g)(3t) = -9$t^{2}$ + 3t + 5