Question

tổng S = 1 . 200 + 2 . 199 + 3 . 198 + 4 . 197 + ........ + 199 . 2 + 200 .1

please help me

Answer 1

=1*200+2*(200-1)+3*(200-2)+...+199(200-198)+200(200-199)

=(1+2+3+...+200)-(1*2+2*3+...+199*200)

=200*201/2-199*200*201/3

=1353400

Answer 2

Ko ai giúp đâu hehehe.No who help you=))

Answer 3

1-2+3-4+...+198+199

 

Answer 4

a)S1=1-2+3-4+...-198+199.

b)S2=-11+16_21+26+...-1001+1006-1011+1016.