Chapter 3: Problem 43
Find the inverse function of \(f\). \(f(x)=4-x^{2}, \quad x \geq 0\)
Short Answer
Expert verified
The inverse function is \(f^{-1}(x) = \sqrt{4 - x}\).
Step by step solution
01
Replace f(x) with y
Start by writing the equation in terms of y. Replace \(f(x)\) with \(y\) in the given function: \(y = 4 - x^2\). This makes it easier to solve for the inverse.
02
Solve for x
We manipulate the equation to solve for \(x\). First, subtract 4 from both sides: \(y - 4 = -x^2\). Then, multiply both sides by -1 to eliminate the negative: \(-y + 4 = x^2\), or \(x^2 = 4 - y\).
03
Take the square root
Since the value of \(x\) is non-negative, we only consider the positive root. Take the square root of both sides: \(x = \sqrt{4 - y}\).
04
Swap x and y
To find the inverse, we swap \(x\) and \(y\). So, the inverse function is obtained: \(y = \sqrt{4 - x}\).
05
Write the inverse function
The inverse function of \(f(x)\) is denoted by \(f^{-1}(x)\). Therefore, \(f^{-1}(x) = \sqrt{4 - x}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Functions
Quadratic functions are a key topic in algebra. They are expressed in the form \(f(x) = ax^2 + bx + c\), where \(a\), \(b\), and \(c\) are constants and \(a eq 0\). The defining feature here is the presence of the squared term, \(x^2\), which creates a parabolic graph. These graphs are symmetric and can open upwards or downwards depending on the sign of \(a\). For instance, in our original function \(f(x) = 4 - x^2\), we see a quadratic expression where the graph opens downwards, since the coefficient of \(x^2\) is negative.
Key properties of quadratic functions include:
Key properties of quadratic functions include:
- The vertex form, \(f(x) = a(x - h)^2 + k\), where \((h, k)\) is the vertex of the parabola.
- The axis of symmetry, which is a vertical line through the vertex, given by \(x = h\).
- The parabola opens upwards if \(a > 0\) and downward if \(a < 0\).
Domain and Range
The domain and range of a function are fundamental concepts representing the input and output values a function can accept. The domain of a function refers to all possible 'x' values that you can substitute into the function, while the range refers to all possible 'y' values the function can produce.
For \(f(x) = 4 - x^2\) with \(x \geq 0\):
For \(f(x) = 4 - x^2\) with \(x \geq 0\):
- The domain is \([0, \infty)\) because \(x\) must be greater than or equal to zero. This restriction is vital when finding the inverse, as it ensures that we work within the function's limits.
- The range for \(f(x)\) is \((-\infty, 4]\), because \(f(x)\) produces values from 4 down to negative infinity as \(x\) increases within its domain.
Square Root Functions
Square root functions belong to a category that involves the square root operation, typically expressed as \(f(x) = \sqrt{x}\). For these functions, it's crucial to consider domain restrictions to maintain the function's definition on real numbers. Generally, the expression inside the square root must be non-negative.
In the context of our inverse function, \(f^{-1}(x) = \sqrt{4 - x}\), we observe:
In the context of our inverse function, \(f^{-1}(x) = \sqrt{4 - x}\), we observe:
- The domain is \(x \leq 4\), because we cannot take the square root of a negative number and expect a real result. Thus, \(4 - x \geq 0\).
- The range is \([0, \, \infty)\), reflecting that the square root function outputs non-negative values.