Question

Tính giá trị của

S=1x2 + 2x3 + 3x4 + 4x5 + ... + 99x100

Answer 1

Gọi biểu thức trên là A, ta có :

A = 1x2 + 2x3 + 3x4 + 4x5 + ...+ 99x100

A x 3 = 1x2x3 + 2x3x3 + 3x4x3 + 4x5x3 + ... + 99x100x3

A x 3 = 1x2x3 + 2x3x(4-1) + 3x4x(5-2) + 4x5x(6-3) + ... + 99x100x(101-98)

A x 3 = 1x2x3 + 2x3x4 - 1x2x3 + 3x4x5 - 2x3x4 + 4x5x6 - 3x4x5 + ... + 99x100x101 - 98x99x100.

A x 3 = 99x100x101

A = 99x100x101 : 3

 

A = 333300

Answer 2

Gọi biểu thức trên là S, ta có :

S = 1x2 + 2x3 + 3x4 + 4x5 + ...+ 99x100

S x 3 = 1x2x3 + 2x3x3 + 3x4x3 + 4x5x3 + ... + 99x100x3

S x 3 = 1x2x3 + 2x3x(4-1) + 3x4x(5-2) + 4x5x(6-3) + ... + 99x100x(101-98)

S x 3 = 1x2x3 + 2x3x4 - 1x2x3 + 3x4x5 - 2x3x4 + 4x5x6 - 3x4x5 + ... + 99x100x101 - 98x99x100.

S x 3 = 99x100x101

S = 99x100x101 : 3

S = 333300

 

Answer 3

=333300

k nha nha nha nha

mik k lại cho
 

Answer 4

S = 1x2 + 2x3 + 3x4 + 4x5 + ... + 99x100

3S = 1x2x3 + 2x3x3 + 3x4x3 + 4x5x3 + ... + 99x100x3

3S = 1x2x3 + 2x3x(4-1) + 3x4x(5-2) + 4x5x(6-3) + ... +99x100x(101-98)

3S = 1x2x3 + 2x3x4 - 1x2x3 + 3x4x5 - 2x3x4 + 4x5x6 - 3x4x5 + ... + 99x100x101 - 98.99.100

S = 99x100x101 : 3

S =333300

Answer 5

S=333300

Answer 6

333300

Answer 7

S = 333300.

Đúng 100% luôn!

Ai tk cho mình mình tk lại.

Answer 8

333300

CHÚC BẠN HỌC GIỎI

Answer 9

333300

Answer 10

=333300 nhé bạn

Answer 11

sao lai ax3 nghia la sao ha cac bn mk ko mhieu giup mk nha

Answer 12

A = 1x2 + 2x3 + 3x4 + 4x5 + ... + 99x100

=> 3A = 1x2x3 + 2x3x3 + 3x4x3 + 4x5x3 + ... + 99x100x3

=> 3A = 1x2x3 + 2x3x(4-1) + 3x4x(5-2) + 4x5x(6-3) + ... +99x100x(101-98)

=> 3A = 1x2x3 + 2x3x4 - 1x2x3 + 3x4x5 - 2x3x4 + 4x5x6 - 3x4x5 + ... + 99x100x101 - 98.99.100

=> A = 99x100x101 : 3

=> A =333300 

Answer 13

có S rồi đặt A cc

bị ngu hết sao mà k nó đúng

Answer 14

vì sao có 3A

Answer 15

S = 1x2 + 2x3 + 3x4 + 4x5 + ...+ 99x100

S x 3 = 1x2x3 + 2x3x3 + 3x4x3 + 4x5x3 + ... + 99x100x3

S x 3 = 1x2x3 + 2x3x(4-1) + 3x4x(5-2) + 4x5x(6-3) + ... + 99x100x(101-98)

S x 3 = 1x2x3 + 2x3x4 - 1x2x3 + 3x4x5 - 2x3x4 + 4x5x6 - 3x4x5 + ... + 99x100x101 - 98x99x100.

S x 3 = 99x100x101

S = 99x100x101 : 3

S = 333300

Answer 16

Gọi biểu thức trên là A, ta có :

A = 1x2 + 2x3 + 3x4 + 4x5 + ...+ 99x100

A x 3 = 1x2x3 + 2x3x3 + 3x4x3 + 4x5x3 + ... + 99x100x3

A x 3 = 1x2x3 + 2x3x(4-1) + 3x4x(5-2) + 4x5x(6-3) + ... + 99x100x(101-98)

A x 3 = 1x2x3 + 2x3x4 - 1x2x3 + 3x4x5 - 2x3x4 + 4x5x6 - 3x4x5 + ... + 99x100x101 - 98x99x100.

A x 3 = 99x100x101

A = 99x100x101 : 3

A = 333300

Answer 17

S = 1 + (1x2+2) + (2x3+3) + (3x4+4) +...+ (99x100+100).

S = 12 + 22 + 32 + 42 +...+ 1002 - (1+100) x 100 : 2.

S = 100 x (100+1) x (2x100+1) : 6 - 101 x 100 :2.

S = 333300

Answer 18

A x 3 ở đâu thế ?????? 

Answer 19

333300

Answer 20

S = 1 x 2 + 2 x 3 + ... + 99 x 100

3S = 1 x 2 x 3 + 2 x 3 x 3 + ... + 99 x 100 x 3

= 1 x 2 x ( 3 - 0 ) + 2 x 3 x ( 4 - 1 ) + ... + 99 x 100 x ( 101 - 98 )

= 1 x 2 x 3 - 1 x 2 x 0 + 2 x 3 x 4 - 2 x 3 x 1 + .... 99 x 100 x 101 - 98 x 99 x 100

= 1 x 2 x 0 + 99 x 100 x 101

S = 99 x 100 x 101 : 3

= 333300  

Answer 21

S = 1.2 + 2.3 + ... + 99.100 

3S = 1.2.3 + 2.3.3 + ... + 99.100.3 

3S = 1.2. ( 3 + 0 ) + 2.3 ( 4 - 1 ) + ... + 99.100. ( 101 - 98 ) 

3S = 1.2.3 + 2.3.4 - 1.2.3 + ... + 99.100.101 - 98.99.100

3S = 99.100.101

S = 333300

Vậy S = 333300

Answer 22

Đặt A

Gọi biểu thức trên là A, ta có :

A = 1x2 + 2x3 + 3x4 + 4x5 + ...+ 99x100

A x 3 = 1x2x3 + 2x3x3 + 3x4x3 + 4x5x3 + ... + 99x100x3

A x 3 = 1x2x3 + 2x3x(4-1) + 3x4x(5-2) + 4x5x(6-3) + ... + 99x100x(101-98)

A x 3 = 1x2x3 + 2x3x4 - 1x2x3 + 3x4x5 - 2x3x4 + 4x5x6 - 3x4x5 + ... + 99x100x101 - 98x99x100.

A x 3 = 99x100x101

A = 99x100x101 : 3

A = 333300

Answer 23

Tại sao 2 vế nhân với 3