Câu a:

1 + {-2 - [-3 + (-4 + |x|)]} = 1 - 2 + [(-3 - 4)]

1 + {-2 -[-3 - 4 + |x|]} = 1 - 2 + [-7]

1 + {-2 - [- 7 + |x|]} = 1 - 2 - 7

1 + {- 2 + 7 - |x|} = - 1 - 7

1 + {5 - |x|} = - 8

5 - |x| = - 8 - 1

5 - |x| = - 9

|x| = 5 + 9

|x| = 14

x = - 14 hoặc x = 14

Vậy x ∈ {-14; 14}

Câu b:

34 + (9 - 21) = 3417 - (x + 3417)

34 + (-12) = 3417 - x - 3417

34 - 12 = 3417 - 3417 - x

22 = - x

x = 22 : (-1)

x = - 22

Vậy x = - 22

\(\dfrac{48}{25}\cdot\dfrac{27}{55}+2\dfrac{4}{9}\cdot\dfrac{14}{33}\)

\(=\dfrac{1296}{1375}+\dfrac{22}{9}\cdot\dfrac{14}{33}\\ =\dfrac{1296}{1375}+\dfrac{28}{27}\\ =\dfrac{34992}{37125}+\dfrac{38500}{37125}\\ =\dfrac{73492}{37125}\)

\(1\dfrac{19}{22}\cdot\left(\dfrac{47}{77}-\dfrac{16}{15}\right)\\ =\dfrac{41}{22}\cdot\dfrac{-527}{1155}\\ =\dfrac{-21607}{25410}\)

\(\left(3\dfrac{10}{99}+4\dfrac{11}{99}-5\dfrac{8}{299}\right)-\left(\dfrac{1}{2}-\dfrac{1}{3}-\dfrac{1}{6}\right)\\ =\left(\dfrac{307}{99}+\dfrac{37}{99}-\dfrac{1503}{299}\right)-0\\ =\dfrac{344}{99}-\dfrac{1053}{299}\\ =-\dfrac{107}{2277}\)

\(Tìmx:\)

\(a.x:3\frac{1}{15}=1\frac{1}{12}.\)

        \(x:\frac{46}{15}=\frac{13}{12}.\)

                 \(x=\frac{13}{12}.\frac{46}{15}.\)

                  \(x=\frac{299}{90}.\)          

\(Tính:\)

\(a.\frac{41}{42}+\frac{55}{56}+\frac{71}{72}+\frac{89}{90}BCNN=2520.\)  \(=\frac{2460}{2520}+\frac{2475}{2520}+\frac{2485}{2520}+\frac{2492}{2520}.\)

\(=\frac{9912}{2520}.\)

\(=\frac{59}{15}.\)

CÂU B CỦA BÀI TÌM X MÌNH CHƯA HỌC NÊN KO BÍT LÀM!

a) x : \(3\frac{1}{5}=1\frac{1}{12}\)

x : \(\frac{16}{5}=\frac{13}{12}\)

x = \(\frac{13}{12}.\)\(\frac{16}{5}\)

x = \(\frac{208}{60}=\frac{52}{15}\)

b) x + 15% . x = 115

x + \(\frac{3}{20}\).x = 115

x.1 + \(\frac{3}{20}.x=115\)

x. (1+\(\frac{3}{20}\))=115

x. \(\frac{23}{20}=115\)

x = \(115:\frac{23}{20}\)

x=100

Câu a:

18 - |x - 1| = 2^2

18 - |x - 1| = 4

|x - 1| = 18 - 4

|x - 1| = 14

x - 1 = -14 hoặc x - 1 = 14

Th1: x - 1 = -14

x = - 14 + 1

x = -13

Th2: x - 1 = 14

x = 14 + 1

x = 15

Vậy x ∈ {-13; 15}

Câu b:

x - {55 - [49 + (-28 - x)]} = 13 - {47 + [25 - (32 - x)]}

x - {55 - [49 - 28 - x]} = 13 - {47 + [25 - 32 + x]}

x - {55 - 49 + 28 + x} = 13 - {47 + 25 - 32 + x}

x - {6 + 28 + x} = 13 - {72 - 32 + x}

x - {34 + x} = 13 - {40 + x}

x - 34 - x = 13 - 40 - x

(x - x) + x = 13 - 40 + 34

0 + x = - 27 + 34

x = 7

Vậy x = 7

Hack nao

\(\left[\dfrac{4}{9}+\left(\dfrac{3}{8}x.\left(-\dfrac{1}{2}\right)\right)\right].\dfrac{6}{11}=\dfrac{18}{55}\)

\(\Rightarrow\)\(\left[\dfrac{4}{9}+\left(\dfrac{3}{8}x.\left(-\dfrac{1}{2}\right)\right)\right]=\dfrac{18}{55}:\dfrac{6}{11}\)

\(\Rightarrow\dfrac{4}{9}+\dfrac{3}{8}x.\dfrac{-1}{2}=\dfrac{3}{5}\)

\(\Rightarrow\dfrac{3}{8}x.\dfrac{-1}{2}=\dfrac{3}{5}-\dfrac{4}{9}\)

\(\Rightarrow\dfrac{3}{8}x.\dfrac{-1}{2}=\dfrac{7}{45}\)

\(\Rightarrow\dfrac{3}{8}x=\dfrac{7}{45}:\dfrac{-1}{2}\)

\(\Rightarrow\dfrac{3}{8}x=\dfrac{-14}{45}\)

\(\Rightarrow x=\dfrac{-112}{135}\)

\(\dfrac{4}{9}+\left[\dfrac{3}{8}x.\left(-\dfrac{1}{2}\right)\right].\dfrac{6}{11}=\dfrac{18}{55}\)

\(\Leftrightarrow\dfrac{4}{9}+\left(-\dfrac{3}{16}x\right).\dfrac{6}{11}=\dfrac{18}{55}\)

\(\Leftrightarrow-\dfrac{3}{16}x.\dfrac{6}{11}=\dfrac{18}{55}-\dfrac{4}{9}\)

\(\Leftrightarrow-\dfrac{3}{16}x.\dfrac{6}{11}=-\dfrac{58}{495}\)

\(\Leftrightarrow-\dfrac{3}{16}x=-\dfrac{58}{495}:\dfrac{6}{11}=-\dfrac{29}{135}\)

\(\Leftrightarrow x=-\dfrac{29}{135}:\left(-\dfrac{3}{16}\right)=\dfrac{464}{405}\)

\(A=\frac{16}{3.7}+\frac{16}{7.11}+...+\frac{16}{95.99}\)

\(\Leftrightarrow\frac{1}{4}A=\frac{1}{3}-\frac{1}{99}=\frac{32}{99}\)

\(\Rightarrow A=\frac{32}{99}:\frac{1}{4}=\frac{128}{99}\)

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