Question

Tính F = 1 + 3 + 6 + 10 +...+ 4851 + 4950

Answer 1

F=1+3+10+.....+4851+4950

2F=2+6+12+20+.....+9702+9900

2F=1.2+2.3+3.4+4.5+.........+98.99+99.100

xét A=1.2+2.3+3.4+4.5+.....+98.99+99.100

3A=1.2.3+2.3.4-1.2.3+3.4.5-2.3.4+..+99.100.101-98.99.100

3A=99.100.101

A=333300

Thay A vào F ta có:

2F=333300

F=333300:2=166650

TICK NHA nOBITA kUN

Answer 2

mới học

2F = 2+6+12+20+...+9702+9900 = 1.2+2.3+3.4+4.5+...+99.100

2F = 33.100.101

F=33.50.101=166650