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28 tháng 7 2019

\(E=\frac{\frac{1}{3}-\frac{1}{7}-\frac{1}{13}}{\frac{2}{3}-\frac{2}{7}-\frac{2}{13}}.\frac{\frac{3}{4}-\frac{3}{16}-\frac{3}{64}-\frac{3}{256}}{1-\frac{1}{4}-\frac{1}{16}-\frac{1}{64}}\)

\(=\frac{\frac{1}{3}-\frac{1}{7}-\frac{1}{13}}{2.\left(\frac{1}{3}-\frac{1}{7}-\frac{1}{13}\right)}.\frac{3.\left(\frac{1}{4}-\frac{1}{16}-\frac{1}{64}-\frac{1}{256}\right)}{4.\left(\frac{1}{4}-\frac{1}{16}-\frac{1}{64}-\frac{1}{256}\right)}\)

\(=\frac{1}{2}.\frac{3}{4}\)

\(=\frac{3}{8}\)

Bài 1 : Thực hiện phép tính(1) D = \(1+\frac{1}{2}\left(1+2\right)+\frac{1}{3}\left(1+2+3\right)+...+\frac{1}{16}\left(1+2+...+16\right)\)(2) M =\(\frac{\frac{1}{99}+\frac{2}{98}+\frac{3}{97}+...+\frac{99}{1}}{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{100}}\)Bài 2 : Tìm x biết(1) \(x-\left\{x-\left[x-\left(-x+1\right)\right]\right\}=1\)(2) \(\left[\frac{1}{2}+\frac{1}{3}+...+\frac{1}{2016}\right]\cdot...
Đọc tiếp

Bài 1 : Thực hiện phép tính

(1) D = \(1+\frac{1}{2}\left(1+2\right)+\frac{1}{3}\left(1+2+3\right)+...+\frac{1}{16}\left(1+2+...+16\right)\)

(2) M =\(\frac{\frac{1}{99}+\frac{2}{98}+\frac{3}{97}+...+\frac{99}{1}}{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{100}}\)

Bài 2 : Tìm x biết

(1) \(x-\left\{x-\left[x-\left(-x+1\right)\right]\right\}=1\)

(2) \(\left[\frac{1}{2}+\frac{1}{3}+...+\frac{1}{2016}\right]\cdot x=\frac{2015}{1}+\frac{2014}{2}+...+\frac{1}{2015}\)

(3) \(\frac{x}{\left(a+5\right)\left(4-a\right)}=\frac{1}{a+5}+\frac{1}{4-a}\)

(4) \(\frac{x+2}{11}+\frac{x+2}{12}+\frac{x+2}{13}=\frac{x+2}{14}+\frac{x+2}{15}\)

(5) \(\frac{x+1}{2015}+\frac{x+2}{2014}+\frac{x+3}{2013}+\frac{x+4}{2012}+4=0\)

Bài 3 : 

(1) Cho : A =\(\frac{9}{1}+\frac{8}{2}+\frac{7}{3}+...+\frac{1}{9}\); B =\(\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{10}\)

CMR : \(\frac{A}{B}\)Là 1 số nguyên

(2) Cho : D =\(\frac{1}{1001}+\frac{1}{1002}+\frac{1}{1003}+...+\frac{1}{2000}\)CMR : \(D< \frac{3}{4}\)

Bài 4 : Ký hiệu [x] là số nguyên lớn nhất không vượt quá x , gọi là phần nguyên của x.

VD : [1.5] =1 ; [3] =3 ; [-3.5] = -4

(1) Tính :\(\left[\frac{100}{3}\right]+\left[\frac{100}{3^2}\right]+\left[\frac{100}{3^3}\right]+\left[\frac{100}{3^4}\right]\)

(2) So sánh : A =\(\left[X\right]+\left[X+\frac{1}{5}\right]+\left[X+\frac{2}{5}\right]+\left[X+\frac{3}{5}\right]+\left[X+\frac{4}{5}\right]\)và B = [5x]. Biết x=3.7

0
1 tháng 11 2020

a)\(=\frac{27}{23}+\frac{5}{21}-\frac{4}{23}+\frac{1}{2}\)+\(\frac{16}{21}\)

\(=\left(\frac{27}{23}-\frac{4}{23}\right)+\left(\frac{5}{21}+\frac{16}{21}\right)\)+\(\frac{1}{2}\)

\(=1+1+\frac{1}{2}\)

\(=2+\frac{1}{2}\)=\(\frac{5}{2}\)

1 tháng 11 2020

DỄ THÌ TỰ LÀM ĐI

25 tháng 10 2018

\(a.9\cdot3^2\cdot\frac{1}{81}=\frac{3^2.3^2.1}{3^4}=\frac{3^4}{3^4}=1\)

\(b.2\frac{1}{2}+\frac{4}{7}:\left(\frac{-8}{9}\right)\)

\(=\frac{5}{2}+\frac{4}{7}.\left(\frac{-9}{8}\right)\)

\(=\frac{5}{2}+\frac{-9}{14}=\frac{13}{7}\)

\(c.3,75.\left(7,2\right)+2,8.\left(3,75\right)\)

\(=3,75.\left(7,2+2,8\right)\)

\(=3,75.10=37,5\)

\(d.\left(\frac{-5}{13}\right).\frac{3}{7}+\left(\frac{-8}{13}\right).\frac{3}{7}+\left(\frac{-4}{7}\right)\)

\(=\frac{3}{7}.\left[\left(\frac{-5}{13}\right)+\left(\frac{-8}{13}\right)\right]+\left(\frac{-4}{7}\right)\)

\(=\frac{3}{7}.\left(-1\right)+\frac{-4}{7}\)

\(=\frac{-3}{7}+-\frac{4}{7}=-1\)

\(e.\sqrt{81}-\frac{1}{8}.\sqrt{64}+\sqrt{0,04}\)

\(=9-\frac{1}{8}.8+0,2\)

\(=9-1+0,2=8+0,2=8,2\)

25 tháng 10 2018

\(a-c\left(tựlm\right)\)

\(b.\left(x-1\right)^5=-32\)

\(\Rightarrow\left(x-1\right)^5=\left(-2\right)^5\)

\(\Rightarrow x-1=-2\)

\(x=-2+1=-1\)

\(d.\left(2^3:4\right).2^{x+1}=64\)

\(2.2^{x+1}=64\)

\(\Rightarrow2^{1+x+1}=64=2^6\)

\(\Rightarrow2+x=6\Rightarrow x=6-2=4\)

30 tháng 6 2019

a) 4x + 1/3 = 3/4

=> 4x = 3/4 - 1/3

=> 4x = 5/12

=> x = 5/12 : 4

=> x = 5/48

b) 1/3 - 2/5 + 3x = 3/4

=> -1/15 + 3x = 3/4

=> 3x = 3/4 + 1/15

=> 3x = 49/60

=> x = 49/ 60 : 3

=> x = 49/180

c) 3(1/2 - x) + 1/3 = 7/6 - x

=> 3/2 - 3x + 1/3 = 7/6 - x

=> 11/6 - 3x = 7/6 - x

=> 11/6 - 7/6 = -x + 3x

=> 2/3 = 2x

=> x = 2/3 : 2

=> x = 1/3

a) \(4x+\frac{1}{3}=\frac{3}{4}\)

\(4x=\frac{3}{4}-\frac{1}{3}\)

\(4x=\frac{9}{12}-\frac{4}{12}\)

\(4x=\frac{5}{12}\)

\(x=\frac{5}{12}:\frac{4}{1}=\frac{5}{12}.\frac{1}{4}\)

\(x=\frac{5}{48}\)

30 tháng 7 2018

d) 

\(\left(\frac{7^3\left(7-1\right)}{7^6}\right)^2\)

\(=\left(\frac{6}{7^3}\right)^2\)

\(=\frac{6^2}{7^{3^2}}\)

\(=\frac{36}{7^6}\)

30 tháng 7 2018

\(\left(\frac{7^3\left(7-1\right)}{7^6}\right)^2\)

\(=\left(\frac{6}{7^3}\right)^2\)

\(=\left(\frac{6^2}{7^{3^2}}\right)\)

\(=\frac{36}{7^6}\)

Code : Breacker