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PROBLEM

(2 points)
Let f(x)=7+x9f(x)=7+\sqrt{x-9}. Then find each of the following, giving all domain
(a) f1(x)=f^{-1}(x)= \square
(b) The domain of ff is \square
(c) The domain of f1f^{-1} is \square
(d) The range of ff is \square
(e) The range of f1f^{-1} is \square

STEP 1

1. We are given the function f(x)=7+x9 f(x) = 7 + \sqrt{x-9} .
2. We need to find the inverse function f1(x) f^{-1}(x) .
3. We need to determine the domain and range of both f f and f1 f^{-1} .

STEP 2

1. Determine the domain of f(x) f(x) .
2. Find the inverse function f1(x) f^{-1}(x) .
3. Determine the domain of f1(x) f^{-1}(x) .
4. Determine the range of f(x) f(x) .
5. Determine the range of f1(x) f^{-1}(x) .

STEP 3

To find the domain of f(x)=7+x9 f(x) = 7 + \sqrt{x-9} , we need the expression under the square root to be non-negative:
x90 x - 9 \geq 0 Solve for x x :
x9 x \geq 9 Thus, the domain of f f is:
[9,) [9, \infty)

STEP 4

To find the inverse function f1(x) f^{-1}(x) , start by setting y=f(x) y = f(x) :
y=7+x9 y = 7 + \sqrt{x-9} Solve for x x in terms of y y :
y7=x9 y - 7 = \sqrt{x-9} Square both sides:
(y7)2=x9 (y - 7)^2 = x - 9 Solve for x x :
x=(y7)2+9 x = (y - 7)^2 + 9 Thus, the inverse function is:
f1(x)=(x7)2+9 f^{-1}(x) = (x - 7)^2 + 9

STEP 5

The domain of f1(x) f^{-1}(x) is the range of f(x) f(x) . From the expression for f(x)=7+x9 f(x) = 7 + \sqrt{x-9} , the smallest value occurs when x=9 x = 9 , giving:
f(9)=7+99=7 f(9) = 7 + \sqrt{9-9} = 7 Since the square root function can take any non-negative value, the range of f(x) f(x) is:
[7,) [7, \infty) Thus, the domain of f1 f^{-1} is:
[7,) [7, \infty)

STEP 6

The range of f(x) f(x) was determined in the previous step as:
[7,) [7, \infty)

SOLUTION

The range of f1(x) f^{-1}(x) is the domain of f(x) f(x) , which is:
[9,) [9, \infty) The solutions are:
(a) f1(x)=(x7)2+9 f^{-1}(x) = (x - 7)^2 + 9
(b) The domain of f f is [9,) [9, \infty)
(c) The domain of f1 f^{-1} is [7,) [7, \infty)
(d) The range of f f is [7,) [7, \infty)
(e) The range of f1 f^{-1} is [9,) [9, \infty)

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