Maths Olympiad Prep

Library / /85 of 520

Algebra Difficulty 5.1 AIME, harder Find the answer

List 5 Use the relationship between the domain and range of inverse functions to find the range of the function y=3x22x2+1y=\frac{3 x^{2}-2}{x^{2}+1} (x0)(x \geqslant 0).

Translate the above text into English, please retain the original text's line breaks and format, and output the translation result directly.

Solution

Solve: From y=3x22x2+1y=\frac{3 x^{2}-2}{x^{2}+1}, we get x2=2+y3yx^{2}=\frac{2+y}{3-y}. Since x0x \geqslant 0, we have x=2+y3yx=\sqrt{\frac{2+y}{3-y}}, so f1(x)=2+x3xf^{-1}(x)=\sqrt{\frac{2+x}{3-x}}. From 2+x3x0\frac{2+x}{3-x} \geqslant 0, we get 2x<3-2 \leqslant x<3, so the domain of the inverse function is [2,3)[-2,3), hence the range of the original function is [2,3)[-2,3).

Want a route through all this instead of an archive? The track puts 2,000 problems in a working order, from AMC 10 level to the IMO shortlist.

Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic and difficulty added by this site.