Question

A=1.2+2.3+3.4+...+1001.1002

Giải giúp mk chiều nay nộp rùi

Answer 1

3A = 1.2.3 + 2.3.(4-1) + ... + 1001.1002.(1003-1000)

3A = 1.2.3 + 2.3.4 - 1.2.3 + ... + 1001.1002.1003 - 1000.1001.1002

3A = 1001.1002.1003

A = 335337002

Dài quá, to quá =))

Học tốt ^^

Answer 2

A=1.2+2.3+3.4+...+1001.1002

3A = 1.2.3 + 2.3.(4-1) + 3.4.(5-2) + ...+ 1001 . 1002 . (1003 - 1000)

3A =  1.2.3 + 2.3.4 - 1.2.3 + 3.4.5 - 2.3.4 + ... + 1001.1002.1003 - 1000 . 1001.1002

= 1001.1002.1003

= 1006011006

Answer 3

       A = 1 x 2 + 2 x 3 + 3 x 4 + ... + 1001 x 1002

=> 3A = 1 x 2 x 3 + 2 x 3 x 3 + 3 x 4 x 3 + ... + 1001 x 1002 x 3

=> 3A = 1 x 2 x ( 3 - 0 ) + 2 x 3 x ( 4 - 1 ) + 3 x 4 x ( 5 - 2 ) + ... + 1001 x 1002 x ( 1003 - 1000 )

=> 3A = 1 x 2 x 3 - 1 x 2 x 0 + 2 x 3 x 4 - 2 x 3 x 1 + 3 x 4 x 5 - 3 x 4 x 2 + ... + 1001 x 1002 x 1003 - 1001 x 1002 x 1000

=> 3A = 1001 x 1002 x 1003

=>   A = ( 1001 x 1002 x 1003 ) : 3

=>   A = ?

Answer 4

2A=2.3+3.4+4.5+...+1002.1003

2A-A=1003-1.2

A=1001