chung minh rang 1/3 -1 /3^2 + 3/3^3 -4/3^4+...+99/3^99-100/3^100 < 3/16
tìm chữ số tận cùng
7^1991
5^1992
chung minh rang
51^n + 47^102 chia het cho 10
19^1991+11^1980 chia het 10
12^1980-2^1000 chia hết cho 10
Chung minh rang
a) \(2018^{102}-2012^{102}chiahetcho10\)
b)\(3^{n+1+2}chiahetcho3\) (n thuoc N*)
c) \(24^{2n+1}+76\) chia het cho 100
Chung minh rang 5n+7 chia het cho3n+2
Cau 1:Tinh A=1/4.9 + 1/9.14 + 1/14.19 + ... + 1/64.69
Cau 2:a.Tim STN nho nhat,biet rang so do khi chia cho 3,cho4,cho 5,cho 6 deu du la 2,con chia cho 7 thi du 3.
b.Tim 2 STN biet tong UCLN va BCNN cua chung = 23
c.Tim STN x;y biet 32x1y chia het cho 45
chung minh 1-1/2+1/3-1/4+1/5-1/6+...+1/19-1/20=1/11+1/12+1/13+...+1/20.
chỉ giùm nha, mik đang cần rât rất là gấp
Chứng minh rằng: \(S=\dfrac{1}{19}+\dfrac{1}{19^2}+\dfrac{1}{19^3}+...+\dfrac{1}{19^{10}}< \dfrac{1}{18}\)
bai 1. 11/3.40/13+37/5:7/33-(11/13.1/3+33/7:5/2)
bai 2.tim x
a,3.(x-1)-5.(-7)=(-2)^3-2x
b,2./(1-x)^2+1/-2^2.3=8
bai 3,cho bieu thuc
M=n+1/n+1 - 3-8n/n+1 + 8/n+1
tim cac gia tri cua n de bieu thuc M co gia tri la so nguyen
bai 4,So hoc sinh cua 1 truong ko qua 1000 em,neuxeptoan bo so hoc sinh cua truong do thanh cac hang,moi hang 20 nguoi thi con thieu 5 nguoi,neu xep moi hang 25 nguoi hoac 30 nguoi thi deu thua 15 nguoi , neu xep 42 hang thi vua du . hoi truong do co bao nhieu hoc sinh
bai 5,cho bieu thuc
A=2+2^2+...+2^200
c/m rang
a, A+2 la 1 luy thua cua 2
b, Achia het cho 30
c,A co phai la so chinh phuong ko ? vi sao ?
bai 6,cho 2 bieu thuc
A=1/1+2 + 1/1+2+3 + ...1/1+2+3+...+99
B=1 + 1/2^2+1/3^2 + ...+1/49^2
c/m rang A<B
chung to A = a^3 + 5a chia het cho 6 neu a thuoc N
