Question

A=\(2\cdot4+4\cdot6+6\cdot8+...+98\cdot100\)(Làm 2 cách nha làm ơn giúp mình với)

 

 

Answer 1

A= 2.2.2+ 2.2.2.2.2+ 2.2.2.2.2.2.2+ ..........+ 2.2.2.2.2.2.2.2..2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2..2.2= tu lam

Answer 2

Cách 1 :

A = 2.4 + 4.6 + 6.8 + ... + 98.100

6.A = 2.4.6 + 4.6.6 + 6.8.6 +...+ 98.100.6

6.A = 2.4.6 + 4.6.( 8 - 2 ) + 6.8.( 10 - 4 ) +...+ 98.100.( 102 - 96 )

6.A = 2.4.6 + 4.6.8 - 2.4.6 + 6.8.10 - 4.6.8 + ... + 98.100.102 - 96.98.100

6.A = ( 2.4.6 - 2.4.6 ) + ( 4.6.8 - 4.6.8 ) + ( 6.8.10 - 6.8.10 ) + ... + ( 96.98.100 - 96.98.100 ) + 98.100.102

6.A = 98.100.102

A = 98.100.102 : 6 = 166600

Cách 2 ( mik chịu )