A = ( 1/4 + ... + 1/7 ) + (1/8+ ... + 1/11 ) + ( 1/12 + ... + 1/15 ) < ( 1/4 + ... + 1/4 ) + ( 1/8 + ... + 1/8 ) + ( 1/12 + ... + 1/12 )
A < 11/6
A = ( 1/4 + ... + 1/9 ) + ( 1/10 + 1/15 ) > ( 1/9 + ... + 1/9 ) + ( 1/15 + ... + 1/15 )
A > 16/15
16/15 < A < 11/6
Vậy 1 < A < 2
Vậy A không thể là giá trị nguyên.
CHO A= 1/4+1/5+1/6+1/20+...+ 1/15. CHUNG TO A KHONG LA SO NGUYEN
CAM ON CAC BAN
CHO A= 1/4+1/5+1/6+1/20+...+1/15. CHUNG TO A KHONG LA SO NGUYEN
CAM ON CAC BAN
CHO A= 1/4+1/5+1/6+1/20+...+ 1/15. CHUNG TO A KHONG LA SO NGUYEN
AI BIET GIAI GIUP MINH NHE
CAM ON CAC BAN NHIEU !
cho A=2*3*5*7*9*......*Pn la tich cua aso nguyen to dau tien. Chung to rang 3 so A-1;A;A+1 KHONG CO SO NAO LA SO CHINH PHUONG
Bai 1: a)Tim so tu nhien a biet 1960va2002 chia cho a cung co so du la 28
b)Tim 2 sop tu nhien a va b , biet :BCNN(a,b)=300;UCLN(a,b)=15 va a+15=b
Bai 2:a)Tong sau la binh phuong so nao ?
S=1+3+5+7+...+199
b) Cho so ab va so ababab
1)chung to ababab la boi cua ab
2)So 3 va 10101 co phai la uoc cua ababab khong , vi sao?
Bai 3
a)Hay viet them dang sau so 664 ba chu so de nhan duoc sdo co 6 chu so chia het cho 5,9,11
b)Tim so nguyen x thuoc Z biet rang :
(x^2-1)(x^2-4)<0
Bai 4 :tim so nguyen x va y biet: xy-x+2y=3
1, biet abb chia het cho 7 chung minh a+2b chia het cho 7
2, cho p la 1 so nguyen to lon hon 3 , p+2 cung la so nguyen to. chung minh p+1 chia het cho 6
Voi n la so tu nhien, cho: A=20134n(2013(4n+3)-1)-1. Chung minh rang A khong phai la so nguyen to.
Cho so a= 36.q + 15 voi q la so tu nhien
A. Chung to rang a khong chia het cho 2
B. Chung to rang a chia het cho 3 va a khong phai la so nguyen to
cho p la so nguyen to lon hon 3
a] chung to rang p 6k+1 hoac 6k+5
b] biet 8p +1 la so nguyen to chung minh 4p+1 la hop so
