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Math

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PROBLEM

Check if f(x)=5x+9f(x)=5x+9 and g(x)=x95g(x)=\frac{x-9}{5} are inverse functions by finding (fg)(x)(f \circ g)(x) and (gf)(x)(g \circ f)(x).

STEP 1

Assumptions1. The function f(x)=5x+9f(x)=5x+9
. The function g(x)=x95g(x)=\frac{x-9}{5}
3. We need to determine if f(x)f(x) and g(x)g(x) are inverse functions. This can be done by checking if (fg)(x)=x(f \circ g)(x) = x and (gf)(x)=x(g \circ f)(x) = x.

STEP 2

First, we will find the composition of ff and gg, denoted as (fg)(x)(f \circ g)(x), which means we substitute g(x)g(x) into f(x)f(x).
(fg)(x)=f(g(x))(f \circ g)(x) = f(g(x))

STEP 3

Substitute g(x)g(x) into f(x)f(x).
(fg)(x)=f(x95)(f \circ g)(x) = f\left(\frac{x-9}{5}\right)

STEP 4

Replace xx in f(x)f(x) with x9\frac{x-9}{}.
(fg)(x)=(x9)+9(f \circ g)(x) =\left(\frac{x-9}{}\right) +9

STEP 5

implify the expression.
(fg)(x)=x9+9(f \circ g)(x) = x -9 +9

STEP 6

Further simplify the expression.
(fg)(x)=x(f \circ g)(x) = x

STEP 7

Now, we will find the composition of gg and ff, denoted as (gf)(x)(g \circ f)(x), which means we substitute f(x)f(x) into g(x)g(x).
(gf)(x)=g(f(x))(g \circ f)(x) = g(f(x))

STEP 8

Substitute f(x)f(x) into g(x)g(x).
(gf)(x)=g(5x+)(g \circ f)(x) = g(5x+)

STEP 9

Replace xx in g(x)g(x) with 5x+95x+9.
(gf)(x)=5x+995(g \circ f)(x) = \frac{5x+9-9}{5}

STEP 10

implify the expression.
(gf)(x)=5x5(g \circ f)(x) = \frac{5x}{5}

STEP 11

Further simplify the expression.
(gf)(x)=x(g \circ f)(x) = x

SOLUTION

Since both (fg)(x)=x(f \circ g)(x) = x and (gf)(x)=x(g \circ f)(x) = x, we can conclude that f(x)f(x) and g(x)g(x) are inverse functions.
Thus, g(x)g(x) is the inverse function of f(x)f(x).

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