Câu hỏi của Huỳnh Thị Mỹ Linh

Question

Cho B=21+22+....+230a. Chứng tỏ B chia hết 21b. Chứng tỏ B chia hết 6c B chia cho 30 dư bao nhiu

Lê Quang Phúc · Accepted Answer

a. B=21+22+....+230=>B=(21+22+23+24+25+26)+(27+28+29+210+211+212)+...+(225+226+227+228+229+230)=>B=(21+22+23+24+25+26)+26.(21+22+23+24+25+26)+...+224.(21+22+23+24+25+26)=>B=126+26.126+...+224.126=>B=126.(1+26+...+224) $⋮$21 vì 126$⋮$21.b)B=21+22+....+230B=(21+22+23+24)+(25+26+27+28)+...+(227+228+229+230)B=(21+22+23+24)+24.(21+22+23+24)+...+226.(21+22+23+24)B=30+24.30+...+226.30B=30.(1+24+...+226) $⋮$6 vì 30 $⋮$6.c)B=21+22+....+230B=(21+22+23+24)+(25+26+27+28)+...+(227+228+229+230)B=(21+22+23+24)+24.(21+22+23+24)+...+226.(21+22+23+24)B=30+24.30+...+226.30B=30.(1+24+...+226) $⋮$30 vì 30 $⋮$30 => B chia 30 dư 0.Câu trả lời: a. B=21+22+....+230=>B=(21+22+23+24+25+26)+(27+28+29+210+211+212)+...+(225+226+227+228+229+230)=>B=(21+22+23+24+25+26)+26.(21+22+23+24+25+26)+...+224.(21+22+23+24+25+26)=>B=126+26.126+...+224.126=>B=126.(1+26+...+224) $⋮$21 vì 126$⋮$21.b)B=21+22+....+230B=(21+22+23+24)+(25+26+27+28)+...+(227+228+229+230)B=(21+22+23+24)+24.(21+22+23+24)+...+226.(21+22+23+24)B=30+24.30+...+226.30B=30.(1+24+...+226) $⋮$6 vì 30 $⋮$6.c)B=21+22+....+230B=(21+22+23+24)+(25+26+27+28)+...+(227+228+229+230)B=(21+22+23+24)+24.(21+22+23+24)+...+226.(21+22+23+24)B=30+24.30+...+226.30B=30.(1+24+...+226) $⋮$30 vì 30 $⋮$30 => B chia 30 dư 0.

๖ACE✪Hoàngミ★Việtツ · Answer

a. B=21+22+....+230<=>B=(21+22+23+24+25+26)+(27+28+29+210+211+212)+...+(225+226+227+228+229+230)<=>B=(21+22+23+24+25+26)+26.(21+22+23+24+25+26)+...+224.(21+22+23+24+25+26)<=>B=126+26.126+...+224.126<=>B=126.(1+26+...+224) ⋮21 vì 126⋮21.b)B=21+22+....+230B=(21+22+23+24)+(25+26+27+28)+...+(227+228+229+230)B=(21+22+23+24)+24.(21+22+23+24)+...+226.(21+22+23+24)B=30+24.30+...+226.30B=30.(1+24+...+226) ⋮6 vì 30 ⋮6.c)B=21+22+....+230B=(21+22+23+24)+(25+26+27+28)+...+(227+228+229+230)B=(21+22+23+24)+24.(21+22+23+24)+...+226.(21+22+23+24)B=30+24.30+...+226.30B=30.(1+24+...+226) ⋮30 vì 30 Câu trả lời: a. B=21+22+....+230<=>B=(21+22+23+24+25+26)+(27+28+29+210+211+212)+...+(225+226+227+228+229+230)<=>B=(21+22+23+24+25+26)+26.(21+22+23+24+25+26)+...+224.(21+22+23+24+25+26)<=>B=126+26.126+...+224.126<=>B=126.(1+26+...+224) ⋮21 vì 126⋮21.b)B=21+22+....+230B=(21+22+23+24)+(25+26+27+28)+...+(227+228+229+230)B=(21+22+23+24)+24.(21+22+23+24)+...+226.(21+22+23+24)B=30+24.30+...+226.30B=30.(1+24+...+226) ⋮6 vì 30 ⋮6.c)B=21+22+....+230B=(21+22+23+24)+(25+26+27+28)+...+(227+228+229+230)B=(21+22+23+24)+24.(21+22+23+24)+...+226.(21+22+23+24)B=30+24.30+...+226.30B=30.(1+24+...+226) ⋮30 vì 30

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