b: \(x+\dfrac{5}{6}=\dfrac{3}{8}\)

=>\(x=\dfrac{3}{8}-\dfrac{5}{6}\)

=>\(x=\dfrac{9}{24}-\dfrac{20}{24}=-\dfrac{11}{24}\)

c: \(\dfrac{2}{3}x-\dfrac{1}{2}=\dfrac{5}{6}\)

=>\(\dfrac{2}{3}x=\dfrac{5}{6}+\dfrac{1}{2}=\dfrac{8}{6}=\dfrac{4}{3}\)

=>2x=4

=>x=4/2=2

d: \(\dfrac{x}{7}=\dfrac{6}{-21}\)

=>\(\dfrac{x}{7}=\dfrac{-2}{7}\)

=>x=-2

e: \(\left(\dfrac{7}{3}x-0,6\right):\dfrac{3^2}{5}=1\)

=>\(\dfrac{7}{3}x-0,6=\dfrac{3^2}{5}=1,8\)

=>\(\dfrac{7}{3}x=2,4\)

=>\(x=2,4:\dfrac{7}{3}=2.4\cdot\dfrac{3}{7}=\dfrac{7.2}{7}=\dfrac{36}{35}\)

f: \(\dfrac{x}{45}=\dfrac{5}{6}+\dfrac{-29}{30}\)

=>\(\dfrac{x}{45}=\dfrac{25}{30}-\dfrac{29}{30}=-\dfrac{4}{30}=-\dfrac{2}{15}\)

=>\(x=-\dfrac{2}{15}\cdot45=-6\)

g: \(\left(4,5-2x\right)\cdot\left(-\dfrac{1^4}{7}\right)=\dfrac{11}{14}\)

=>\(4,5-2x=\dfrac{11}{14}:\dfrac{-1}{7}=\dfrac{-11}{2}\)

=>\(2x=4,5+\dfrac{11}{2}=\dfrac{20}{2}=10\)

=>x=10/2=5

h: \(-\dfrac{2}{7}+\dfrac{4}{7}x=\dfrac{5}{7}\)

=>\(\dfrac{4}{7}x=\dfrac{5}{7}+\dfrac{2}{7}=\dfrac{7}{7}\)

=>4x=7

=>\(x=\dfrac{7}{4}\)

a) \(2\frac{1}{2}-\left(q-\frac{1}{2}\right)=\frac{3}{5}\)

\(\Rightarrow q-\frac{1}{2}=2\frac{1}{2}-\frac{3}{5}=\frac{19}{10}\)

\(\Rightarrow q=\frac{19}{10}+\frac{1}{2}=\frac{12}{5}=2,4\)

\(\Rightarrow q=2,4\)

b) \(\frac{1}{3}\cdot q-\frac{1}{5}\cdot q=0,6\)

\(=q\cdot\left(\frac{1}{3}-\frac{1}{5}\right)=0,6\)

\(=q\cdot\frac{2}{15}=0,6\)

\(\Rightarrow q=0,6:\frac{2}{15}=\frac{9}{2}=4,5\)

\(\Rightarrow q=4,5\)

c) \(\frac{3}{5}-q:\frac{1}{2}=\frac{1}{7}\)

\(\Rightarrow q:\frac{1}{2}=\frac{3}{5}-\frac{1}{7}=\frac{16}{35}\)

\(\Rightarrow q=\frac{16}{35}\cdot\frac{1}{2}=\frac{8}{35}\)

\(\Rightarrow q=\frac{5}{35}\)

Ở câu b áp dụng phân phối giữa phép nhân vs phép trừ.

a) \(\left(2x-1\right)+\frac{3}{15}=\frac{3}{2}\)

\(\Rightarrow2x-1=\frac{3}{2}-\frac{3}{15}=\frac{13}{10}\)

\(\Rightarrow2x=\frac{13}{10}+1=\frac{23}{10}\)

\(\Rightarrow x=\frac{23}{20}\)

b) \(x+\frac{46}{15}=1,5\)

\(\Rightarrow x+\frac{46}{15}=\frac{3}{2}\)

\(\Rightarrow x=\frac{3}{2}-\frac{46}{15}\)

\(\Rightarrow x=\frac{-47}{30}\)

c) \(\left(-2x+1\right)+\frac{3}{15}=\frac{5}{3}\)

\(\Rightarrow-2x+1=\frac{5}{3}-\frac{3}{15}=\frac{22}{15}\)

\(\Rightarrow-2x=\frac{7}{15}\Rightarrow x=\frac{-7}{30}\)

2,8 : ( \(\frac{1}{5}-3x\)) = \(\frac{7}{5}\)

 \(\frac{1}{5}-3x=2,8:\frac{7}{5}\)

 \(\frac{1}{5}-3x=2\)

        \(3x=\frac{1}{5}-2\)

        \(3x=\frac{1}{5}-\frac{10}{5}\)

            \(3x=\frac{-9}{5}\)

             \(x=\frac{-3}{5}\)

Vậy \(x=\frac{-3}{5}\)

2,8 : (1/5 - 3x) = 7.5 

=> 1/5 - 3x = 2,8 : 7/5 = 14/5 . 5/7   ( áp dụng  a:b=c thì b=a:c ấy )

=> 1/5 - 3x=2 

=> 3x= 1/5 - 2= -9/5  ( áp dụng a-b=c thì b= a-c nha )

=> x= -9/5 : 3 = -9/5 . 1/3 = -3/5

1, Thực hiện phép tính

a, (-23).(-3).(+4).(-7)

=69.(-28)

=(-1932)

b, 2.8.(-14).(-3)

=16.42

=672

2, Tìm x

a, 2436 : x = 12                                                                                  b, 6. x - 5 = 613

         x =2436 : 12                                                                                  6. x = 613 + 5 = 618

         x = 203                                                                                              x =618 : 6 = 103

c, 12. (x - 1) = 0                                                                                  d, 0 : x = 0

    x - 1 = 12 : 0 = 0                                                                                      x =  0 : 0

         x = 0 + 1 = 1                                                                                       x = 0

1. 

a) \(\left(-23\right).\left(-3\right).4.\left(-7\right)=[\left(-23\right).\left(-3\right).\left(-7\right)].4\)

\(=-483.4=-1932\)

b) \(=16.42=672\)

2. 

a) \(\Rightarrow x=2436\div12=203\)

b) \(\Rightarrow6x=618\Rightarrow x=103\)

c) \(\Rightarrow x-1=0\Rightarrow x=1\)

d) Ko có gtr nào của x thỏa mãn 0:x=0

~ HỌC TỐT ~

                                            # Q.TRANG #