AMPLE 3 en: \( f(x)=2 x^{2} \) Determine the equation of the inverse of \( f \) in the form \( f^{-1}(x)=\ldots \) On the same set of \( x \)-axis, sketch the graphs of \( f \) and \( f^{-1} \). Indicate clearly the intercepts with the axis, as well as another point on the graph of each f and \( f^{-1} \). Determine the domain and range of both \( f \) and \( f^{-1} \). Is \( f^{-1} \) a function? Give a reason for your answer. How can \( f \) be restricted so that the inverse is a function? On the separate set of axis, sketch both restricted function and their inverses.
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The Deep Dive
To find the inverse of the function \( f(x) = 2x^2 \), start by replacing \( f(x) \) with \( y \): \[ y = 2x^2. \] Then, swap \( x \) and \( y \) to solve for \( y \): \[ x = 2y^2. \] Now, isolate \( y \): \[ y^2 = \frac{x}{2} \quad \Rightarrow \quad y = \sqrt{\frac{x}{2}} \text{ (for } y \geq 0\text{)}. \] Thus the inverse can be written as: \[ f^{-1}(x) = \sqrt{\frac{x}{2}}. \] To sketch the graphs, note that the function \( f(x) = 2x^2 \) is a parabola opening upwards, with its vertex at (0,0) and intercepting the y-axis at (0,0). The key point can be chosen as (1, 2). The inverse \( f^{-1}(x) = \sqrt{\frac{x}{2}} \) is defined for \( x \geq 0 \), reaching the point (2, 1) on the graph. The graphs intersect at (0,0). The domain and range of \( f \) are: - Domain of \( f: (-\infty, \infty) \) - Range of \( f: [0, \infty) \) For \( f^{-1} \): - Domain: [0, ∞) - Range: \( (-\infty, \infty) \) Since \( f^{-1}(x) = \sqrt{\frac{x}{2}} \) only returns non-negative outputs, \( f^{-1} \) is a function. To restrict \( f \) to ensure that its inverse is also a function, limit the domain to \( x \geq 0 \). Sketch the restricted function \( f(x) = 2x^2 \) for \( x \geq 0 \) with the vertex at (0,0) and then its inverse \( f^{-1}(x) = \sqrt{\frac{x}{2}} \) on a separate set of axes, showing the specified points clearly.