a.A=1/3+1/6+1/12+1/24+...+1/192+1/384
A=128/384+64/384+32/384+16/384+...+2/384+1/384
A=(128+64+32+16+...+2+1)/384
A=255/384
A=85/128
b.Mình chịu
c.C=1+1/3+1/9+1/27+...+1/729+1/2187
C=1+729/2187+243/2187+81/2187+...+3/2187+1/2187
C=1+(729+243+81+...+3+1)/2187
C=1+1093/2187
C=3280/2187
d.D=2016x2009-2016x1009/2017x999+1017
D=2016x(1009+1000)-2016x1009/2017x999+1017
D=2016x1009+2016x1000-2016x1009/2017x999+1017
D=(2016x1009-2016x1009)+2016x1000/2017x999+1017
D=0+2016x1000/2017x999+1017
D=1