x-y=2014²-2013*2015 =2014²-(2014-1)(2014+1)=2014²-2014²+1=1
2013²-2012*2014=2013²-(2013-1)(2013+1)=2013²-2013²+1²=1
.............................................
5²-4*6= 5²-(5-1)(5+1)=5²-5²+1²=1
4²-3*5=4²-(4-1)*4+1)=...=1
3²-2*4=3²-(3-1)(3+1)=...=1
2²-1*3=.....................=1
1²= 1
avem de insumat 2014de 1 , deci x-y=2014