MathDB
2012 preRMO p13, α=b-c, b=c-d, c=d-a and abcd\ne 0

Source:

June 17, 2019
algebra

Problem Statement

If a=bc,b=cd,c=daa=b-c, b=c-d, c=d-a and abcd0abcd\ne 0, then what is the value of ab+bc+cd+da\frac{a}{b}+\frac{b}{c}+\frac{c}{d}+\frac{d}{a}?