a) Cho \(\dfrac{a}{b}\)=\(\dfrac{b}{c}\)=\(\dfrac{c}{d}\)
CMR:(\(\dfrac{a+b+c}{b+c+d}\))\(^3\)=\(\dfrac{a}{d}\)
b)Cho \(\dfrac{a1}{a2}\)=\(\dfrac{a2}{a3}\)=\(\dfrac{a3}{a4}\)=...=\(\dfrac{a2008}{a2009}\)
CMR: \(\dfrac{a1}{a2009}\)=(\(\dfrac{a1+a2+a3+...+a2008}{a2+a3+a4+...+a2009}\))\(^{2008}\)
c) Cho \(\dfrac{a}{2003}\)=\(\dfrac{b}{2004}\)=\(\dfrac{c}{2005}\)
CMR: 4(a-b)(b-c)=(c-a)\(^2\)