Question

B=1.2+2.3+3.4+...+99.100

 

Answer 1

B=1.2+2.3+3.4+...+99.100

=>3B=1.2.3+2.3.3+3.4.3+...+99.100.3

=>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 = 99.100.101:3 = 333300

Answer 2

Đặt B = 1.2 + 2.3 + 3.4 + ... + 99.100

3B = 1.2.3 + 2.3.4 + 3.4.3 + ... + 99.100.3

3B = 1.2(3-0)+2.3(4-1)+3.4(5-2). .... . 99.100 ( 101 - 98 )

3B = (1.2.3 + 2.3.4 + 3.4.5 + .. + 99.100.101) - (0.1.2 + 1.2.3 + 2.3.4 + ... + 98.99.100)

3B = 99.100.101 - 0.1.2

3B = 999900 - 0

3B = 999900

  B = 999900 : 3

  B = 333300

Answer 3

thank you

Answer 4

 B = 1.2 + 2.3 + 3.4 + ... + 99.100

3B = 1.2.3 + 2.3.4 + 3.4.3 + ... + 99.100.3

3B = 1.2(3-0)+2.3(4-1)+3.4(5-2). .... . 99.100 ( 101 - 98 )

3B = (1.2.3 + 2.3.4 + 3.4.5 + .. + 99.100.101) - (0.1.2 + 1.2.3 + 2.3.4 + ... + 98.99.100)

3B = 99.100.101 - 0.1.2

3B = 999900 - 0

3B = 999900

  B = 999900 : 3

  B = 333300

Answer 5

B=1.2+2.3+3.4+...+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

\(B=\frac{99.100.101}{3}\)

\(B=33.100.101\)

\(B=333300\)

KL:...................