Question

Tính tổng : N = 1 + 3 + 6 + 10 + ... + 4851 + 4950

Answer 1

mình bít làm nè

k nha

Answer 2

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

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

Xét B= 1.2+2.3+3.4+4.5+...+98.99+99.100

3B=1.2.3+2.3.(4-1)+3.4.(5-2)+...+99.100.(101-98)

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

3B=99.100.101

B= 333300

Thay B vào A, ta được:

2A= 333300

A= 166650

Answer 3

Đây nhé bạn, nhớ k cho mình nha

A=1+3+6+10+...+4851+4950A=1+3+6+10+...+4851+4950

2A=2+6+12+20+...+9702+99002A=2+6+12+20+...+9702+9900

2A=1.2+2.3+3.4+4.5+...+98.99+99.1002A=1.2+2.3+3.4+4.5+...+98.99+99.100

Xét B=1.2+2.3+3.4+4.5+...+98.99+99.100B=1.2+2.3+3.4+4.5+...+98.99+99.100

3B=1.2.3+2.3(4−1)+3.4(5−2)+...+99.100(101−98)3B=1.2.3+2.3(4−1)+3.4(5−2)+...+99.100(101−98)

3B=1.2.3+2.3.4−1.2.3+3.4.5−2.3.4+...+99.100.101−98.99.1003B=1.2.3+2.3.4−1.2.3+3.4.5−2.3.4+...+99.100.101−98.99.100

3B=99.100.1013B=99.100.101

B=333300B=333300

Thay BB vào AA ta được:

2A=3333002A=333300

A=166650A=166650

Answer 4

Tính tổng : N = 1 + 3 + 6 + 10 + ... + 4851 + 4950

A=1+3+6+10+...+4851+4950A=1+3+6+10+...+4851+4950

2A=2+6+12+20+...+9702+99002A=2+6+12+20+...+9702+9900

2A=1.2+2.3+3.4+4.5+...+98.99+99.1002A=1.2+2.3+3.4+4.5+...+98.99+99.100

Xét B=1.2+2.3+3.4+4.5+...+98.99+99.100B=1.2+2.3+3.4+4.5+...+98.99+99.100

3B=1.2.3+2.3(4−1)+3.4(5−2)+...+99.100(101−98)3B=1.2.3+2.3(4−1)+3.4(5−2)+...+99.100(101−98)

3B=1.2.3+2.3.4−1.2.3+3.4.5−2.3.4+...+99.100.101−98.99.1003B=1.2.3+2.3.4−1.2.3+3.4.5−2.3.4+...+99.100.101−98.99.100

3B=99.100.1013B=99.100.101

B=333300B=333300

Thay BB vào AA ta được:

2A=3333002A=333300

A=166650A=166650

Answer 5

A=1+3+6+10+...+4851+4950

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

Xét B=1.2+2.3+3.4+4.5+...+98.99+99.100

3B=1.2.3+2.3(4−1)+3.4(5−2)+...+99.100(101−98)

3B=1.2.3+2.3.4−1.2.3+3.4.5−2.3.4+...+99.100.101−98.99.100

3B=99.100.1013

B=333300

Thay B vào A ta được:

2A=333300

A=166650