MÀ KHOAN ULTR

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1)\(1\frac{3}{4}-1\frac{3}{8}:\left(\frac{3}{8}+\frac{9}{20}\right)=\frac{7}{4}-\frac{11}{8}:\frac{33}{40}=\frac{7}{4}-\frac{5}{3}=\frac{1}{12}\)

D

D

\(4\dfrac{3}{8}+5\dfrac{2}{3}=\dfrac{4\times8+3}{8}+\dfrac{5\times3+2}{3}\\ =\dfrac{35}{8}+\dfrac{17}{3}=\dfrac{35\times3+17\times8}{24}=\dfrac{241}{24}\\ ----\\ 2\dfrac{3}{8}+1\dfrac{1}{4}=\dfrac{2\times8+3}{8}+\dfrac{1\times4+1}{4}=\dfrac{19}{8}+\dfrac{5}{4}\\ =\dfrac{19+5\times2}{8}=\dfrac{29}{8}\\ ----\\ 2\dfrac{3}{8}-1\dfrac{1}{4}+5\dfrac{1}{3}=\left(2-1+5\right)+\left(\dfrac{3}{8}-\dfrac{1}{4}+\dfrac{1}{3}\right)\\ =6+\dfrac{3\times3-1\times6+1\times8}{24}\\ =6+\dfrac{11}{24}=6\dfrac{11}{24}\)

10

Chọn C

C

a: ta có: \(7-\left(2x-\frac13\right)^2=3\)

=>\(\left(2x-\frac13\right)^2=7-3=4\)

=>\(\left[\begin{array}{l}2x-\frac13=2\\ 2x-\frac13=-2\end{array}\right.\Rightarrow\left[\begin{array}{l}2x=2+\frac13=\frac73\\ 2x=-2+\frac13=-\frac53\end{array}\right.\)

=>\(\left[\begin{array}{l}x=\frac73:2=\frac76\\ x=-\frac53:2=-\frac56\end{array}\right.\)

b: \(\left(2x+\frac13\right)^2-\frac38=\frac18\)

=>\(\left(2x+\frac13\right)^2=\frac38+\frac18=\frac48=\frac12\)

=>\(2x+\frac13=\sqrt{\frac12}=\frac{\sqrt2}{2}\)

=>\(2x=\frac{\sqrt2}{2}-\frac13=\frac{3\sqrt2-2}{6}\)

=>\(x=\frac{3\sqrt2-2}{12}\)

c: \(12:\left\lbrack29-\left(x-\frac23\right)^2\right\rbrack=3\)

=>\(29-\left(x-\frac23\right)^2=12:3=4\)

=>\(\left(x-\frac23\right)^2=29-4=25\)

=>\(\left[\begin{array}{l}x-\frac23=5\\ x-\frac23=-5\end{array}\right.\Rightarrow\left[\begin{array}{l}x=5+\frac23=\frac{17}{3}\\ x=-5+\frac23=-\frac{13}{3}\end{array}\right.\)

d: \(\left(3x-\frac12\right)^3+\frac83=\frac{29}{9}-\frac{14}{27}\)

=>\(\left(3x-\frac12\right)^3+\frac83=\frac{87}{27}-\frac{14}{27}=\frac{73}{27}\)

=>\(\left(3x-\frac12\right)^3=\frac{73}{27}-\frac83=\frac{73}{27}-\frac{72}{27}=\frac{1}{27}=\left(\frac13\right)^3\)

=>\(3x-\frac12=\frac13\)

=>\(3x=\frac12+\frac13=\frac56\)

=>\(x=\frac{5}{18}\)

e: \(2\left(2x-\frac13\right)^2+\frac43=\frac56+\frac{13}{18}\)

=>\(2\left(2x-\frac13\right)^2=\frac{15}{18}+\frac{13}{18}-\frac43=\frac{28}{18}-\frac{24}{18}=\frac{4}{18}=\frac29\)

=>\(\left(2x-\frac13\right)^2=\frac19\)

=>\(\left[\begin{array}{l}2x-\frac13=\frac13\\ 2x-\frac13=-\frac13\end{array}\right.\Rightarrow\left[\begin{array}{l}2x=\frac23\\ 2x=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=\frac13\\ x=0\end{array}\right.\)

a) \(4\dfrac{3}{8}+5\dfrac{2}{3}\)

\(=\dfrac{35}{8}+\dfrac{17}{3}\)

\(=\dfrac{105}{24}+\dfrac{136}{24}\)

\(=\dfrac{241}{24}\)

b) \(2\dfrac{3}{8}+1\dfrac{1}{4}+3\dfrac{6}{7}\)

\(=\dfrac{19}{8}+\dfrac{5}{4}+\dfrac{27}{7}\)

\(=\dfrac{29}{8}+\dfrac{27}{7}\)

\(=\dfrac{419}{56}\)

c) \(2\dfrac{3}{8}-1\dfrac{1}{4}+5\dfrac{1}{3}\)

\(=\dfrac{19}{8}-\dfrac{5}{4}+\dfrac{16}{3}\)

\(=\dfrac{9}{8}+\dfrac{16}{3}\)

\(=\dfrac{155}{24}\)

d) \(\left(\dfrac{5}{2}+\dfrac{1}{3}\right):\left(1-\dfrac{1}{2}\right)\)

\(=\dfrac{17}{6}:\dfrac{1}{2}\)

\(=\dfrac{17}{6}\cdot2\)

\(=\dfrac{17}{3}\)

e) \(\left(\dfrac{5}{2}-\dfrac{1}{3}\right)\cdot\dfrac{9}{2}-\dfrac{6}{7}\)

\(=\dfrac{13}{6}\cdot\dfrac{9}{2}-\dfrac{6}{7}\)

\(=\dfrac{39}{4}-\dfrac{6}{7}\)

\(=\dfrac{249}{28}\)

a: =4+3/8+5+2/3

=9+9/24+16/24

=9+25/24

=216/24+25/24=241/24

b: \(=\dfrac{19}{8}+\dfrac{5}{4}+\dfrac{27}{7}=\dfrac{19+10}{8}+\dfrac{27}{7}\)

=27/7+29/8

=419/56

c: =2+3/8-1-1/4+5+1/3

=6+3/8-1/4+1/3

=6+3/8+1/12

=144/24+9/24+2/24

=155/24

d: =(15/6+2/6):1/2

=17/6*2

=17/3

e: =(15/6-2/6)*9/2-6/7

=13/6*9/2-6/7

=117/12-6/7

=249/28

e. 1/3; 3/8; 1/2; 3/5

sai sai

Lời giải chi tiết:

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