Solved on Dec 06, 2023

Find the value of (fg)(3)(f \circ g)(3) where f(x)=7x24xf(x) = 7x^2 - 4x and g(x)=5x9g(x) = 5x - 9.

STEP 1

Assumptions
1. The function f(x)f(x) is defined as f(x)=7x24xf(x)=7x^2-4x.
2. The function g(x)g(x) is defined as g(x)=5x9g(x)=5x-9.
3. We need to find the value of the composition of ff and gg, denoted as (fg)(x)\left(f \circ g\right)(x), at x=3x=3.

STEP 2

To find the composition (fg)(x)\left(f \circ g\right)(x), we first need to evaluate g(x)g(x) and then apply the result as the input for f(x)f(x).
(fg)(x)=f(g(x))\left(f \circ g\right)(x) = f(g(x))

STEP 3

Evaluate g(x)g(x) at x=3x=3.
g(3)=5(3)9g(3) = 5(3) - 9

STEP 4

Calculate the value of g(3)g(3).
g(3)=159=6g(3) = 15 - 9 = 6

STEP 5

Now that we have g(3)=6g(3) = 6, we will use this value as the input for the function f(x)f(x).
f(g(3))=f(6)f(g(3)) = f(6)

STEP 6

Substitute x=6x=6 into the function f(x)f(x).
f(6)=7(6)24(6)f(6) = 7(6)^2 - 4(6)

STEP 7

Calculate the value of f(6)f(6).
f(6)=7(36)4(6)f(6) = 7(36) - 4(6)

STEP 8

Continue the calculation.
f(6)=25224f(6) = 252 - 24

STEP 9

Finalize the calculation to find f(6)f(6).
f(6)=228f(6) = 228

STEP 10

Thus, the value of (fg)(3)\left(f^{\circ} g\right)(3) is 228228.
The correct answer is D) 228.

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