Maths Olympiad Prep

Library / /181 of 520

Algebra Difficulty 5.0 AIME, harder Find the answer

-、(20 points) Let the real number kk satisfy 0<k<10<k<1. Solve the fractional equation about xx
2kx11x2x=k+1x \frac{2 k}{x-1}-\frac{1}{x^{2}-x}=\frac{k+1}{x} \text {. }

A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

Solution

2kx(x1)x1(x1)x=(k+1)(x1)(x1)x2kx1=(k+1)(x1)(k1)x=k. Also, 0<k<1, so x=kk1. \begin{array}{l} \frac{2 k x}{(x-1) x}-\frac{1}{(x-1) x}=\frac{(k+1)(x-1)}{(x-1) x} \\ \Rightarrow 2 k x-1=(k+1)(x-1) \\ \Rightarrow(k-1) x=-k . \\ \text { Also, } 0<k<1 \text {, so } x=-\frac{k}{k-1} . \end{array}

Upon inspection, when k=12k=\frac{1}{2}, x=1x=1 is an extraneous root, and the original equation has no solution;
(Continued on page 48)
When 0<k<10<k<1, and k12k \neq \frac{1}{2}, the solution to the original equation is
x=kk1. x=-\frac{k}{k-1} .

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.