abc la so co 3 chữ số hay là tích abc

sai đề

Tìm x biết

a, \(\dfrac{x-2}{4}=\dfrac{-16}{2-x}\)

b,\(\dfrac{x+y}{2014}=\dfrac{xy}{2015}=\dfrac{x-y}{2016}\)

Tính

a, \(\left(\dfrac{1999}{2011}-\dfrac{2011}{1999}\right)-\left(\dfrac{-12}{1999}-\dfrac{12}{2011}\right)\)

b, \(\left(1-\dfrac{1}{2}\right).\left(1-\dfrac{1}{3}\right).\left(1-\dfrac{1}{4}\right).....\left(1-\dfrac{1}{2015}\right)\)