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\(2)x-17+x=x-7\)

\(x+x-x=-7+17\)

\(x=-10\)

Vậy ....

âm 10 , nhỉ ?

a) 31 - 2 ( x + 3 ) = 21

           2 ( x + 3 ) = 31 - 21

           2 ( x + 3 ) = 10

                x + 3    = 10 : 2

                x + 3     = 5

                 x          = 5 - 3

                 x = 2

b) ( x - 11 ) : 7 + 5 = 7

     ( x - 11 ) : 7       = 7 - 5

      ( x - 11 ) : 7      = 2

      ( x - 11 )           = 2 x 7

        x - 11             = 14

        x                    = 14 + 11

        x  = 25

b) ( x - 11 ) : 7 + 5 = 7

     ( x - 11 ) : 7       = 7 - 5

      ( x - 11 ) : 7      = 2

      ( x - 11 )           = 2 x 7

        x - 11             = 14

        x                    = 14 + 11

        x  = 25

a) \(\left(x-1\right)^3=8=2^3\)

\(x-1=2\)

\(x=2+1=3\)

b) \(7^{2x-6}=49=7^2\)

\(2x-6=2\)

\(2x=6+2=8\)

\(x=8:2=4\)

c) \(\left(2x-14\right)^7=128=2^7\)

\(2x-14=2\)

\(2x=14+2=16\)

\(x=16:2=8\)

d) \(x^4\cdot x^5=5^3\cdot5^6=5^4\cdot5^5\)

\(x=5\)

e) \(3\cdot\left(x+2\right):7\cdot4=120\)

\(x+2=120:3\cdot7:4\)

\(x+2=70\)

\(x=70-2=68\)

Lời giải:

a. $(x-1)^3=8=2^3$
$\Rightarrow x-1=2$

$\Rightarrow x=3$

b. $7^{2x-6}=49=7^2$
$\Rightarrow 2x-6=2$

$\Rightarrow 2x=8$

$\Rightarrow x=4$

c. $(2x-14)^7=128=2^7$

$\Rightarrow 2x-14=2$

$\Rightarrow 2x=16$

$\Rightarrow x=18$

d.

$x^4.x^5=5^3.5^6$

$x^9=5^9$

$\Rightarrow x=5$

e. 

$3(x+2):7=120:4=30$

$3(x+2)=30.7=210$

$x+2=210:3=70$

$x=70-2=68$

Tìm x:

\(a.\frac{2}{3}+x=\frac{5}{7}+\frac{7}{17}\div\frac{49}{34}\)

     \(\frac{2}{3}+x=1\)

               \(x=1-\frac{2}{3}\)

               \(x=\frac{1}{3}.\)

\(b.x-\frac{4}{6}+\frac{5}{9}=\frac{28}{45}\)

               \(x-\frac{4}{6}=\frac{28}{45}-\frac{5}{9}\)

               \(x-\frac{4}{6}=\frac{1}{15}\)

                         \(x=\frac{1}{15}+\frac{4}{6}\)

                         \(x=\frac{11}{15}.\)

\(c.x\div\frac{6}{7}+\frac{2}{3}=\frac{7}{3}\)

              \(x\div\frac{6}{7}=\frac{7}{3}-\frac{2}{3}\)

              \(x\div\frac{6}{7}=\frac{5}{3}\)

                        \(x=\frac{5}{3}\times\frac{6}{7}\)

                        \(x=\frac{30}{21}.\)

\(d.\frac{15}{21}\div x=\frac{3}{7}+\frac{2008}{2009}\times\frac{2000}{2008}+\frac{9}{2008}\times\frac{2008}{2009}\)

       \(\frac{5}{7}\div x=\frac{10}{7}\)

                 \(x=\frac{10}{7}\times\frac{5}{7}\)

                 \(x=\frac{50}{49}.\)

Bài 3 là hỗn số hả em?

Bài 1: 

a) Ta có: \(\dfrac{2}{5}\cdot x+\dfrac{1}{3}=\dfrac{1}{5}\)

\(\Leftrightarrow\dfrac{2}{5}\cdot x=\dfrac{1}{5}-\dfrac{1}{3}=\dfrac{-2}{15}\)

\(\Leftrightarrow x=\dfrac{-2}{15}:\dfrac{2}{5}=\dfrac{-2}{15}\cdot\dfrac{5}{2}\)

hay \(x=-\dfrac{1}{3}\)

Vậy: \(x=-\dfrac{1}{3}\)

b) Ta có: \(\dfrac{1}{5}+\dfrac{5}{3}:x=\dfrac{1}{2}\)

\(\Leftrightarrow\dfrac{5}{3}:x=\dfrac{1}{2}-\dfrac{1}{5}=\dfrac{3}{10}\)

\(\Leftrightarrow x=\dfrac{5}{3}:\dfrac{3}{10}=\dfrac{5}{3}\cdot\dfrac{10}{3}\)

hay \(x=\dfrac{50}{9}\)

Vậy: \(x=\dfrac{50}{9}\)

c) Ta có: \(\dfrac{4}{9}-\dfrac{5}{3}\cdot x=-2\)

\(\Leftrightarrow\dfrac{5}{3}x=\dfrac{4}{9}+2=\dfrac{22}{9}\)

\(\Leftrightarrow x=\dfrac{22}{9}:\dfrac{5}{3}=\dfrac{22}{9}\cdot\dfrac{3}{5}\)

hay \(x=\dfrac{22}{15}\)

Vậy: \(x=\dfrac{22}{15}\)

d) Ta có: \(\dfrac{5}{7}:x-3=\dfrac{-2}{7}\)

\(\Leftrightarrow\dfrac{5}{7}:x=\dfrac{-2}{7}+3=\dfrac{19}{21}\)

\(\Leftrightarrow x=\dfrac{5}{7}:\dfrac{19}{21}=\dfrac{5}{7}\cdot\dfrac{21}{19}\)

hay \(x=\dfrac{15}{19}\)

Vậy:\(x=\dfrac{15}{19}\)