4+12+24+40+...+19404+19800=???
4+12+24+40+...+19404+19800
4+12+24+40+...+19404+19800
A=4+12+24+40+...19404+19800
a=4+12+24+40+...+19404+19800
A=4+12+24+40+...+19404+19800
D=4+12+24+40+.............+19404+19800
Tính:
4+12+24+40+...+19404+19800=?
Tính :
A = 4 + 12 + 24 + 40 + .......+ 19404 + 19800 .