Porisma

A hint to get started

A restricted parabola and its inverse

The function ff is defined by f:x↦(x−4)2+1f:x\mapsto(x-4)^2+1 for x∈Rx\in\mathbb R, x>4x>4.

(i) Sketch the graph of y=f(x)y=f(x). Your sketch should indicate the position of the graph in relation to the origin.

(ii) Find f−1(x)f^{-1}(x), stating the domain of f−1f^{-1}.

(iii) On the same diagram as in part (i), sketch the graph of y=f−1(x)y=f^{-1}(x).

(iv) Write down the equation of the line in which the graph of y=f(x)y=f(x) must be reflected in order to obtain the graph of y=f−1(x)y=f^{-1}(x), and hence find the exact solution of the equation f(x)=f−1(x)f(x)=f^{-1}(x).

[2008/II/4]

CJC · Functions · Discussion 2 · 2025

Use the original restricted domain to select the square-root branch.

Read the worked solution