y1=1,y2=1,y3=-2,y4=-2,y5=3,y6=3,y7=-4,y8=-4,y9=5
(2)y1+y2+...+y9=1+1-2-2+3+3-4-4+5=5
(3)y1+y2+.+y2012+y2013
每8个为一循环,即有y1+...+y8=0
2013/8=251...5
故有y1+y2+...+y2013=y2009+y2010+y2011+y2012+y2013
=(2*2009-1)+4017-4018-4018+4025
=4023
y1=1,y2=1,y3=-2,y4=-2,y5=3,y6=3,y7=-4,y8=-4,y9=5
(2)y1+y2+...+y9=1+1-2-2+3+3-4-4+5=5
(3)y1+y2+.+y2012+y2013
每8个为一循环,即有y1+...+y8=0
2013/8=251...5
故有y1+y2+...+y2013=y2009+y2010+y2011+y2012+y2013
=(2*2009-1)+4017-4018-4018+4025
=4023