a) \(A=\frac{7}{10}+\frac{7}{10^2}+\frac{7}{10^3}+...\)
\(A=\frac{777...}{1000...}\)
b) 1/2+1/3+1/4+…+1/63=1/2+(1/3+1/4)+(1/5+1/6+…+1/10)+(1/11+1/12+….+1/20)+(1/21+1/22+….1/63).
Ta thấy:
1/3+1/4>1/4+1/4=1/2
1/5+1/6+…+1/10>5/10=1/2
1/11+1/12+….+1/20>10/20=1/2
Thêm.cái 1/2 sắn có là đủ >2 rồi nhể
a)\(\frac{7}{x}<\frac{x}{4}<\frac{10}{x}\)
b) Cho A=\(\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+...+\frac{1}{9^2}\). Chứng tỏ: \(\frac{8}{9}>A>\frac{2}{5}\)
Bài 1:Tìm \(x\in Z\)biết
\(A=\frac{3}{x-1}\)\(B=\frac{x-2}{x+3}\)\(C=\frac{2x+1}{x-3}\)
Bài 2:Chứng tỏ rằng:
\(A=\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+.....+\frac{1}{63}>2\)\(B=\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+\frac{1}{5^2}+\frac{1}{6^2}+\frac{1}{7^2}+\frac{1}{8^2}< 1\)
Bài 3:Tính hợp lí
\(A=\frac{\frac{3}{5}+\frac{3}{7}-\frac{3}{11}}{\frac{4}{5}+\frac{4}{7}-\frac{4}{11}}\)
\(B=\frac{7}{4}\left(\frac{3333}{1212}+\frac{3333}{2020}+\frac{3333}{3030}+\frac{3333}{4242}\right)\)
Cho A = \(1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}\)
B = \(\left(1+\frac{1}{2}+\frac{1}{3}+...+\frac{1}{10}\right)-2\left(\frac{1}{2}+\frac{1}{4}+...+\frac{1}{10}\right)\)
a) So sánh A và B
b) Chứng minh A = \(\frac{1}{6}+\frac{1}{7}+\frac{1}{8}+\frac{1}{9}+\frac{1}{10}\)
\(A=\frac{\frac{2}{5}-\frac{2}{7}+\frac{3}{11}}{\frac{7}{5}-\frac{7}{9}+\frac{7}{11}}:\frac{\frac{1}{3}-\frac{1}{4}+\frac{1}{5}}{\frac{7}{6}-\frac{7}{8}+\frac{7}{10}}\)
a)Tìm A
b)tìm x biết A . x + \(\frac{5}{6}\) = \(-\frac{3}{4}\)
\(A=2\frac{3}{7}:\left(-12\frac{1}{2}+15\frac{1}{7}\right).\left(3\frac{3}{10}\right)-\left(\frac{-34}{37}\right).\left(2\frac{1}{10}-4\frac{2}{5}\right)\)
\(B=-3\frac{1}{10}:\left(\frac{1}{2}-\frac{2}{5}\right)-2\frac{1}{28}:\left(\frac{2}{7}-\frac{3}{4}\right)\)
bài 2:Tìm x
a. \(-1\frac{2}{3}-\left|2x-1\right|:\frac{3}{5}=-2\)
b. \(\frac{x-7}{36}=\frac{-4}{7-x}\)
Mình đang cần gấp ai đúng mình tích cho
Mia mình nộp rồi
bài 1 So sánh
a)\(A=\frac{3}{8^3}+\frac{7}{8^4}\) ; \(B=\frac{7}{8^3}+\frac{3}{8^4}\)
b)\(A=\frac{10^{1992}+1}{10^{1991}+1};B=\frac{10^{1993}+1}{10^{1992}+1}\)
c)\(A=\frac{10^7+5}{10^4-8};B=\frac{10^8+6}{10^8-7}\)
d)\(A=\frac{1+5+5^2+...+5^9}{1+5+5^2+...+5^8};B=\frac{1+3+3^2+...+3^9}{1+3+3^2+...+3^8}\)
e)\(A=\frac{2011}{2012}+\frac{2012}{2013};B=\frac{2011+2012}{2012+2013}\)
Hãy so sánh:
a) A= \(\frac{178}{179}+\frac{179}{180}+\frac{183}{181}\)với 3.
b) A= \(\frac{1+5+5^2+5^3+...+5^{10}+5^{11}}{1+5+5^2+5^3+...+5^9+5^{10}}\)và B=\(\frac{1+7+7^2+7^3+...+7^{10}+7^{11}}{1+7+7^2+7^3+...+7^9+7^{10}}\)
Bài 1: Tìm A biết:
\(A=\frac{7}{10}+\frac{7}{10^2}+\frac{7}{10^3}+...\)
Ai giúp mk vs ! các bn giúp mk đi !
1.So sánh A và B:
\(A=\frac{10^{11}-1}{10^{12}-1}\)
\(B=\frac{10^{10}+1}{10^{11}+1}\)
2.tính tổng
A=1+2+22+...+2100
B=3-32+33-3+...+399-3100
C1+52+54+56+...+5200
D=7-74+77+...+7301
E=\(\frac{1}{7}+\frac{1}{7^2}+\frac{1}{7^3}+...+\frac{1}{7^{100}}\)
F=\(0-\frac{4}{\text{5}}+\frac{4}{\text{5}^2}-\frac{4}{\text{5}^3}+...+\frac{4}{\text{5}^{200}}\)
