A=1/120+1/168+...+1/9800
=>A=1/10.12+1/12.14+....+1/98.100
=>2A=2/10.12+2/12.14+...+2/98.100
=>2A=1/5-1/6+1/6-1/7+....+1/49-1/50
=>2A=1/5-1/50
=>2A=9/50
=>A=9/100
tinh tong cac so nghich dao cua cac so sau: 2;6;12;20;30;42;56;72;90;110
cho 2 phan so co tong bang 2015 lan tich cua chung
tinh tong cac phan so nghich dao cua chung
Tim 3 phan so biet tong cac nghich dao cua chung la mot so tu nhien?
Cho 2 phan so co tong bang -3 va tich bang 12/5. Tinh tong cac so nghich dao cua 2 phan so do
cho cac so 10, 40,88,154,238,340 .tinh tong cac so nghich dao cuc cac so do moi cach nhanh nhat.
tim 3 so tu nhien doi mot khac nhau sao cho tong cac nghich dao cua 3 so nay co gia tri la so tu nhien
tim so tu nhien viet dc duoi dang\(c^{b-a}\); biet rang \(1\le a< b< c\)vaa,b,c la cac so tu nhien sao cho tong nghich dao cua chung la mot so tu nhien
1.Tim cac cap so nghich dao cua nhau trong cac cap so
a.0,25va4 b.3.4va4,3 c.2va0.5 d.0.7va7
hay chia cac tren mat dong ho lam 2 nhom nhom 1 gom cac so tu nhie lien tiep va nhom 2 gom cac so con lai sao cho :
a) tong cac so cua nhom 1 bang tong cac chu so cua nhom 2
b) tong cac chu so cua nhom 1 bang tong cac chu so cua nhom 2
c) tong cac chu so cua nhom 1 bang 1 nua tong cac chu so cua nhom 2
