Câu hỏi của Bạch mã hoàng tử

Question

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

Long O Nghẹn · Accepted Answer

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 lamCâu trả lời: 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

༄NguyễnTrungNghĩa༄༂ · Answer

Cách 1 :A = 2.4 + 4.6 + 6.8 + ... + 98.1006.A = 2.4.6 + 4.6.6 + 6.8.6 +...+ 98.100.66.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 - 96.98.1006.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 ) + 98.100.1026.A = 98.100.102A = 98.100.102 : 6 = 166600Cách 2 ( mik chịu )Câu trả lời: Cách 1 :A = 2.4 + 4.6 + 6.8 + ... + 98.1006.A = 2.4.6 + 4.6.6 + 6.8.6 +...+ 98.100.66.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 - 96.98.1006.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 ) + 98.100.1026.A = 98.100.102A = 98.100.102 : 6 = 166600Cách 2 ( mik chịu )

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