\(C=3+3^2+3^3+3^4+3^5+...+3^{60}\)
\(C\cdot3=3^2+3^3+3^4+3^5+..+3^{61}\)
Trừ từng vế cho nhau ta có
\(C\cdot3-C=C\cdot\left(3-1\right)=C\cdot2\)
\(c\cdot2=3^{61}-3\)
C=3+3^2+3^3+3^4+.............+3^60
chung minh C+3 la 1 luy thua cua 3
a) Tinh :102 ; 103;104;105;106
b) Viet moi so sau duoi dang luy thua cua 10 :
1000; 1000000; 1 ti ; 1000000000000
bai 1
a,trong phep chia cho 2 co so du co the bang 0 hoac bang 1 .trong moi phep chia cho 3,cho 4,cho 5,so du co the bang bao nhieu ?
b,dang tong quat cua so chia het cho 2 la 2k ,dang tong quat cua so chia cho 2 du 1 la 2k +1 voi k e N .hay viet dang tong quat cua so chia het cho 3 , so chia cho 3 du 1 ,so chia cho 3 du 2.
Cau 1 : Trong mot cuoc thi co 20 cau hoi , moi cau tra loi dung duoc 10 diem , con sai thi tru 3 diem . 1 hs dat duoc 148 diem . Hoi ban ay tra loi duoc bao nhieu cau dung , bao nhieu cau sai Cau 2 : Tim so bi chia , so chia cua mot phep chia biet rangthuong = 3 va so du = 2 . Tong cua so bi chia , so chia , so du = 76 Cau 3 : Tich cua 2 so la 1692 , neu them 4 dv vao mot thua so thi tich moi la 1880 . Tim 2 so do Co ai biet lam thi chi minh voi 
Tinh tong sau hop li :
A=2+2 mu 2 + 2 mu 3 + ............+2 mu 100
B=1+3 mu 2 + 3 mu 3 + .......... + 3 mu 2009
C = 4+ 4 mu 2 + 4 mu 3 + ...............+ 4 mu n
Giup minh voi sory may minh ko co dau minh dang can gap lam !!!
Chứng minh :
a) \(\frac{1}{3}-\frac{2}{3^2}+\frac{3}{3^3}-\frac{4}{3^4}+...+\frac{99}{3^{99}}-\frac{100}{3^{100}}< \frac{3}{16}\) \(\frac{1}{3}-\frac{2}{3^2}+\frac{3}{3^3}+\frac{4}{4^4}+...+\frac{99}{3^{99}}-\frac{100}{3^{100}}< \frac{3}{16}\)
b)\(\frac{1}{41}+\frac{1}{42}+\frac{1}{43}+...+\frac{1}{79}+\frac{1}{80}< \frac{7}{12}\)
c) Cho \(S=\frac{3}{10}+\frac{3}{11}+\frac{3}{12}+\frac{3}{13}+\frac{3}{14}\)
Chứng minh \(1< S< 2\)
1 trung binh cua 3 so la 75. Neu them so 0 vào bên phải số thu 2 thi thi dc số thu nhat. Neu gap 4 lan so thu hai thi dc so thu 3. Tim 3 so do
Cho C = 1 + 3 + 32 + 33 + 34 + 35 + ... + 311. Chứng minh rằng :
a, C chia hết cho 13. b, C chia hết cho 40.
NHANH NHA MIK ĐANG CẦN GẤP.
Trung binh cong cua 3 so la so be nhat co 3 chu so khac nhau biet so thu 2 bang trung binh cong cua 2 so con lai .so thu 3 hon so thu nhat 14.tim 3 so do
