Math

QuestionFind the inverse of the function f(x)=9+4x9f(x)=9+\sqrt{4x-9} for x9x \geq 9.

Studdy Solution

STEP 1

Assumptions1. The function f(x)f(x) is given as f(x)=9+4x9f(x)=9+\sqrt{4x-9} . We are asked to find the inverse of the function f(x)f(x), denoted as f1(x)f^{-1}(x)3. The domain of the inverse function is x9x \geq9

STEP 2

To find the inverse of a function, we first replace f(x)f(x) with yy. This gives usy=9+4x9y =9+\sqrt{4x-9}

STEP 3

Next, we swap xx and yy. This means we replace every xx with yy and every yy with xx. This gives usx=9+y9x =9+\sqrt{y-9}

STEP 4

Now we need to solve this equation for yy to find f1(x)f^{-1}(x). We start by isolating the square root term. We do this by subtracting9 from both sidesx9=4y9x-9 = \sqrt{4y-9}

STEP 5

Next, we square both sides of the equation to eliminate the square root(x9)2=(4y9)(x-9)^2 = (4y-9)

STEP 6

Expanding the left side of the equation gives usx218x+81=4y9x^2 -18x +81 =4y -9

STEP 7

Next, we isolate yy by adding9 to both sides and then dividing by4y=x218x+904y = \frac{x^2 -18x +90}{4}

STEP 8

Finally, we denote yy as f1(x)f^{-1}(x) to indicate that yy is the inverse of the function f(x)f(x)f1(x)=x218x+904f^{-1}(x) = \frac{x^2 -18x +90}{4}So, the inverse of the function f(x)=+4xf(x)=+\sqrt{4x-} is f1(x)=x218x+904f^{-1}(x) = \frac{x^2 -18x +90}{4} for xx \geq.

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