\(f(x)=\sqrt{5-x}+3\)
Changing this to its inverse requires a few steps.
1. Change \(f(x)\) to \(y\).
This step is pretty simple. We are switching from function notation to y=-notation. \(f(x)=\sqrt{5-x}+3\) changes to \(y=\sqrt{5-x}+3\)
2. Interchange x and y
This step is also quite simple; replace all instances of x with y and all instance of y with x.
\(y=\sqrt{5-x}+3\) changes to \(x=\sqrt{5-y}+3\)
3. Solve for y
This step is the hardest. Transform the equation into the form of y=.
\(x=\sqrt{5-y}+3\) | Subtract 3 on both sides. |
\(x-3=\sqrt{5-y}\) | Square both sides to eliminate the square root. |
\((x-3)^2=\left(\sqrt{5-y}\right)^2\) | Expand the left hand side knowing that \((a-b)^2=a^2-2ab+b^2\). |
\(x^2-6x+9=5-y\) | Subtract 5 from both sides. |
\(-y=x^2-6x+4\) | Divide by -1. |
\(y=-x^2+6x-4\) | |
4. Consider Whether the Inverse is actually a Function
In this case, it is a function, so we are OK.
By definition, \(\sqrt{x^2}=|x|\). I know this because if you graph both functions, the output will be the same.
\(x^2+24=0\) | Subtract 24 from both sides. |
\(x^2=-24\) | Take the square root from both sides. |
\(|x|=\sqrt{-24}\) | The absolute value symbol means that the answer is in its positive and negative forms. |
\(x=\pm\sqrt{-24}\) | Now, let's change the square root to an imaginary form. We can apply the radical rule that \(\sqrt{-a}=\sqrt{-1}\sqrt{a}\) |
\(x=\pm\sqrt{24}\sqrt{-1}\) | We know that by definition, \(i=\sqrt{-1}\) |
\(x=\pm i\sqrt{24}\) | We can simplify the square root of 2 to its simplest radical form. |
\(x=\pm2i\sqrt{6}\) | |
In order to solve for x in this equation, we must perform a multitude of operations.
\(2x-6=\frac{3(10-2x)}{2}+\frac{3+5x}{2}\) | Multiply by 2 on both sides to eliminate the pesky fractions. |
\(4x-12=3(10-2x)+3+5x\) | Distribute the 3 into the term 10-2x. |
\(4x-12=30-6x+3+5x\) | Simplify the right hand side by combining the like terms. |
\(4x-12=-x+33\) | Add x to both sides to get the x's on one side of the equation. |
\(5x-12=33\) | Add 12 to both sides. |
\(5x=45\) | Divide by 5 on both sides of the equation. |
\(x=9\) | |