If f(x) and f^-1(x) are inverse functions of each other and f(x)=2x+5, what is f^-1(8)

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Answer:

\(\text{The value of }f^{-1}(8)\text{ is }\frac{3}{2}\)        

Step-by-step explanation:

Given the function

\(f(x)=2x+5\)

\(\text{we have to find the value of }f^{-1}(8)\)

First we have to find the inverse

Step 1: Put f(x)=y, the equation becomes

\(y=2x+5\)

Step 2: Replace x to y and y to x, we get

\(x=2y+5\)

Step 3: Solve for y and then replace it with \(f^{-1}x\)

\(x-5=2y\)

\(y=\frac{x-5}{2}\)

\(f^{-1}(x)=\frac{x-5}{2}\)

Now substitute x=8, we get

\(f^{-1}(8)=\frac{8-5}{2}=\frac{3}{2}\)

\(\text{hence, the value of }f^{-1}(8)\text{ is }\frac{3}{2}\)