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câu 1 :
\(A=\frac{-7}{12}:\frac{49}{11}\cdot\frac{5}{121}-\frac{7}{6}\) \(B=\frac{1}{8}-\frac{8}{7}:8-3:\frac{3}{4}\cdot-2^3\)
\(A=\frac{-11}{84}\cdot\frac{5}{121}-\frac{7}{6}\) \(B=\frac{1}{8}-\frac{8}{7}:\frac{8}{1}-\frac{3}{1}:\frac{3}{4}\cdot\left(-2^3\right)\)
\(A=\frac{-5}{924}-\frac{7}{6}\) \(B=\frac{1}{8}-\frac{1}{7}-\left(-32\right)\)
\(A=\frac{-361}{308}\) \(B=\frac{-1}{56}-\left(-32\right)\)
\(B=\frac{1791}{56}\)
Câu 2 :
a)\(\frac{22}{7}:x=\frac{11}{7}\) b)\(\left(1-3x\right)\cdot\frac{4}{3}=-2^3\)
\(x=\frac{22}{7}:\frac{11}{7}\) \(\left(1-3x\right)\cdot\frac{4}{3}=-8\)
\(x=2\) \(\left(1-3x\right)=-8:\frac{4}{3}\)
\(\left(1-3x\right)=-6\)
\(3x=-6-1=7\)
\(3x=7:3=\frac{7}{3}\)
c ) bằng \(\frac{27}{5}\)nhé
a) \(1\frac{5}{8}:x-1\frac{1}{4}=2\)
=> \(\frac{13}{8}:x-\frac{5}{4}=2\)
=> \(\frac{13}{8}:x=\frac{13}{4}\)
=> \(x=\frac{13}{8}:\frac{13}{4}=\frac{13}{8}\cdot\frac{4}{13}=\frac{1}{2}\)
b) \(\left(x-\frac{1}{3}\right)^2-\frac{1}{2}=0\)
=> \(\left(x-\frac{1}{3}\right)^2=\frac{1}{2}\)
=> x không thỏa mãn
c) 2(x - 1) = 3x + 1
=> 2x - 2 = 3x + 1
=> 2x - 2 - 3x - 1 = 0
=> 2x - 3x - 2 - 1 = 0
=> -x = 3
=> x = -3
d) \(\frac{-2}{x}=\frac{x}{-8}\)=> x2 = 16 => x = \(\pm\)4
e) |7 - x| + 2x = 11
=> |7 - x| = 11 - 2x
=> 7 - x = 11 - 2x
=> 7 - x - 11 + 2x = 0
=> 7 - 11 - x + 2x = 0
=> -4 + x = 0
=> -4 = -x
=> x = 4
a)=> 13/8 : x-5/4 =2
<=> 13/8 : x= 13/4
<=> x=1/2
b)=>x2 - (1/3)2 = 1/2
=>x2-1/9=1/2
=>x2=11/18
=>x=0.78 (bằng xấp xỉ thôi nhé bạn :33)
c)=>2x-2=3x-1
=>2x-3x=2-1
=>-x=1
=>x=-1
còn 2 câu bạn làm nốt nhé :33
k đúng cho mk nhé!!!!
\(2.THPT\)
\(A=\frac{9}{1.2}+\frac{9}{2.3}+\frac{9}{3.4}+...+\frac{9}{98.99}+\frac{9}{99.100}\)
\(A=9\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{99.100}\right)\)
\(A=9\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{99}-\frac{1}{100}\right)\)
\(A=9\left(1-\frac{1}{100}\right)\)
\(A=9.\frac{99}{100}\)
\(A=\frac{891}{100}\)
\(B=\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}+...+\frac{2}{93.95}\)
\(B=\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+...+\frac{1}{93}-\frac{1}{95}\)
\(B=\frac{1}{5}-\frac{1}{95}\)
\(B=\frac{18}{95}\)
\(D=\frac{5}{2.7}+\frac{4}{7.11}+\frac{3}{11.14}+\frac{1}{14.15}+\frac{13}{15.28}\)
\(D=\frac{1}{2}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{15}+\frac{1}{15}-\frac{1}{28}\)
\(D=\frac{1}{2}-\frac{1}{28}\)
\(D=\frac{13}{28}\)
\(B=3+3^2+3^3+.....+3^{2006}\)
\(\Rightarrow3B=3^2+3^3+....+3^{2007}\)
\(\Rightarrow2B=3^{2007}-3\)
\(\Rightarrow B=\frac{3^{2007}-3}{2}\)
\(2B+3=3^x\)
\(\Rightarrow2.\frac{3^{2007}-3}{2}+3=3^x\)
\(\Rightarrow3^{2007}-3+3=3^x\Rightarrow3^{2007}=3^x\Rightarrow x=2007\)
Ta có: B = 22010 - 22009 - 22008 -......- 2 -1
=> B = 22010 - (1 + 2 + 22 + ..... + 22009)
Đặt A = 1 + 2 + 22 + .... + 22009
=> 2A = 2 + 22 + .... + 22010
=> 2A - A = 22010 - 1
=> A = 22010 - 1
Vậy B = 22010 - (22010 - 1)
=> B = 22010 - 22010 + 1
=> B = 1
Ta có: B = 22010 - 22009 - 22008 -......- 2 -1
=> B = 22010 - (1 + 2 + 22 + ..... + 22009)
Đặt A = 1 + 2 + 22 + .... + 22009
=> 2A = 2 + 22 + .... + 22010
=> 2A - A = 22010 - 1
=> A = 22010 - 1
Vậy B = 22010 - (22010 - 1)
=> B = 22010 - 22010 + 1
=> B = 1
Tự ghi đề nhé!
a. \(\frac{-3}{4}:x=\frac{-11}{36}+\frac{1}{2}\)
= 7/36
x = 7/36 : -3/4 = -7/27
b. \(\orbr{\begin{cases}2x+1=5\\2x+1=-5\end{cases}}\)
Vậy x=2 hoặc x=-3
c. (3-3x)2 = 4
3-3x = 2 hoặc 3-3x = -2
Vậy x= 1/3 hoăc x = 5/3
d. x+2 = 7 hoặc x+2 = -7
Vậy x=5 hoặc x=-9