Math  /  Algebra

Question(A) Find a formula for the inverse of the function f[1](Q)=f(x)=79/x2,x>0f^{[-1]}(Q)=\square \quad f(x)=7-9 / x^{2}, \quad x>0

Studdy Solution

STEP 1

1. We are given the function f(x)=79x2 f(x) = 7 - \frac{9}{x^2} .
2. We need to find the inverse function, denoted as f[1](Q) f^{[-1]}(Q) .
3. The domain of the function is x>0 x > 0 .

STEP 2

1. Set the function equal to Q Q and solve for x x .
2. Rearrange the equation to express x x in terms of Q Q .
3. Verify the domain and range of the inverse function.
4. Write the formula for the inverse function.

STEP 3

Set the function equal to Q Q :
Q=79x2 Q = 7 - \frac{9}{x^2}

STEP 4

Rearrange the equation to solve for x2 x^2 :
Q7=9x2 Q - 7 = -\frac{9}{x^2}
Multiply both sides by 1-1:
7Q=9x2 7 - Q = \frac{9}{x^2}

STEP 5

Solve for x2 x^2 by multiplying both sides by x2 x^2 and dividing by 7Q 7 - Q :
x2=97Q x^2 = \frac{9}{7 - Q}

STEP 6

Take the square root of both sides to solve for x x . Since x>0 x > 0 , we take the positive root:
x=97Q x = \sqrt{\frac{9}{7 - Q}}

STEP 7

Verify the domain and range of the inverse function. Since x>0 x > 0 , 7Q>0 7 - Q > 0 , which implies Q<7 Q < 7 .

STEP 8

Write the formula for the inverse function:
f[1](Q)=97Q f^{[-1]}(Q) = \sqrt{\frac{9}{7 - Q}}
The formula for the inverse function is:
f[1](Q)=97Q f^{[-1]}(Q) = \sqrt{\frac{9}{7 - Q}}

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