Example

Example: Finding the Inverse of the Function f(x)=4x+7f(x) = 4x + 7

To find the inverse of the one-to-one function f(x)=4x+7f(x) = 4x + 7, follow the standard algebraic procedure. Step 1: Substitute yy for f(x)f(x), yielding y=4x+7y = 4x + 7. Step 2: Interchange the variables xx and yy, which results in x=4y+7x = 4y + 7. Step 3: Solve for yy by subtracting 77 from both sides to get x7=4yx - 7 = 4y, and then dividing by 44, resulting in y=x74y = \frac{x - 7}{4}. Step 4: Substitute the inverse notation f1(x)f^{-1}(x) for yy, yielding f1(x)=x74f^{-1}(x) = \frac{x - 7}{4}. Step 5: Verify the functions are inverses by evaluating their compositions. Checking f1(f(x))f^{-1}(f(x)) gives (4x+7)74=4x4=x\frac{(4x + 7) - 7}{4} = \frac{4x}{4} = x. Checking f(f1(x))f(f^{-1}(x)) gives 4(x74)+7=(x7)+7=x4\left(\frac{x - 7}{4}\right) + 7 = (x - 7) + 7 = x. Since both compositions equal xx, the inverse function is confirmed.

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Updated 2026-05-26

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