a) \(\left(x-1\right):3=2^3\) \(\Leftrightarrow\) \(\left(x-1\right):3=8\) \(x+1=24\) \(\Leftrightarrow\) \(x=23\) vậy \(x=23\)

b) \(12-2\left(x+5\right)=-10\) \(\Leftrightarrow\) \(12-2x-10=-10\)

\(\Leftrightarrow\) \(-2x=-12\) \(\Leftrightarrow\) \(x=6\) vậy \(x=6\)

c) \(x-12\left(x+5\right)=-10\) \(\Leftrightarrow\) \(x-12x-60=-10\)

\(\Leftrightarrow\) \(-11x=50\) \(\Leftrightarrow\) \(x=\dfrac{50}{-11}\) vậy \(x=\dfrac{50}{-11}\)

e) \(13-x:2=10\Leftrightarrow-x:2=-3\Leftrightarrow x=\dfrac{3}{2}\)

f) \(\left|12-x\right|-7=5\)

th1 : \(x\le12\) thì \(\left|12-x\right|-7=5\) \(\Leftrightarrow\) \(12-x-7=5\) \(\Leftrightarrow\) \(-x=0\Leftrightarrow x=0\)

th2 : \(x>12\) thì \(\left|12-x\right|-7=5\) \(\Leftrightarrow\) \(x-12-7=5\) \(\Leftrightarrow\) \(x=24\) vậy \(x=0;x=24\)

i) \(x^2-7=2\Leftrightarrow x^2=9\Leftrightarrow x=3\) vậy \(x=3\)

k) \(x^3-4=-12\) \(\Leftrightarrow\) \(x^3=-8\) \(\Leftrightarrow x=-2\) vậy \(x=-2\)

a)\(\left(x-1\right):3=2^3\Rightarrow x-1=2^3.3=24\Rightarrow x=25\)

b)\(12-2\left(x+5\right)=-10\Leftrightarrow12-2x-10=-10\Rightarrow2-2x=-10\Rightarrow2x=12\Rightarrow x=6\)c)\(x-12\left(x+5\right)=-10\Rightarrow x-12x-60=-10\Rightarrow-11x-60=-10\Rightarrow-11x=-70\Rightarrow x=\dfrac{70}{-11}\)d)\(6-\left|x\right|=5\Rightarrow\left|x\right|=1\Rightarrow x=\left\{\pm1\right\}\)

Làm nốt nha

a)\(19\frac{5}{8}:\frac{7}{12}-15\frac{1}{4}:\frac{7}{12}\)

=(\(19\frac{5}{8}-15\frac{1}{4}\)):\(\frac{7}{12}\)

=(\(19\frac{10}{16}-15\frac{4}{16}\)):\(\frac{7}{12}\)

=\(4\frac{6}{16}:\frac{7}{12}\)

=\(\frac{35}{8}:\frac{7}{12}\)

=\(\frac{35}{8}\cdot\frac{12}{7}\)

=\(\frac{15}{2}\)

b)2/5*1/3-2/15:1/5+3/5*1/3

=2/15-2/3+1/5

=-8/15+1/5

=-1/3

aidi qua dong tinh nho h chom minh nhe

  cm bang pp quy nap 
7x5^2n + 12x6^n chia het cho 19 (*) 
(*)dung voi n=1 
gsu (*) dung voi m>=1 
nhu vay 7x5^2m + 12x6^m chia het cho 19 (**) 
ta se cm (*) cung dung voi n=m+1 
that vay 
voi n=m+1 ta co 
7x5^(2m+1) + 12x6^(m+1) 
=25x7x5^2m +12x6x6^m 
=6(7x5^2m+12x6^m) +19 x7x5^2m 
ma theo (**) 7x5^2m +12x6^m chia het cho 19 
vay (*) cung dung khi n=m+1 
=>(*) luon dung voi moi n>=1. dpcm

a :vì 4/7=12/x

4.x=12.7

4.x=84

x=84/4

x=21

a) x-12:(-2)=4

=> x-12=-8

=> x=4
b ) 6-|x| = 5

=> /x/=1

=> x=1;-1
c ) 7⋮ ( x-3)

=> (x-3) thuộc Ư(7)

=> x-3=1 => x=4

=> x-3=-1 => x=2

=> x-3=7 => x= 10

=> x-3=-7 => x=-4

d ) 3⋮ ( 2x+1 )

=> (2x+1) thuộc Ư(3)

=> (2X+1)= 1 => x= 0

=> (2x+1)=-1 => x= -1

=> 2x+1= 3 => x= 1

=> 2x+1=-3 => x= -2

a) \(x-12:\left(-2\right)=4\Rightarrow x-\left(-6\right)=4\Rightarrow x=\left(-6\right)+4=-2\)

b) \(6-\left|x\right|=5\Rightarrow\left|x\right|=6-5=1\Rightarrow x=\left\{\pm1\right\}\)

c)\(7⋮x-3\Rightarrow x-3\inƯ\left(7\right)\)

\(Ư\left(7\right)=\left\{\pm1;\pm7\right\}\)

\(x=\left\{4;2;10;-4\right\}\)

d) \(3⋮2x+1\Rightarrow2x+1\inƯ\left(3\right)\)

\(Ư\left(3\right)=\left\{\pm1;\pm3\right\}\)

\(x\in\left\{0;-1;1;-2\right\}\)

49\(\frac{8}{23}\) - (5\(\frac{7}{32}\) + 14\(\frac{8}{23}\))

= 49\(\frac{8}{23}\) - 5\(\frac{7}{32}\) - 14\(\frac{8}{23}\)

= (49\(\frac{8}{23}\) - 14\(\frac{8}{23}\)) - 5\(\frac{7}{32}\)

= 35 - 5 - \(\frac{7}{32}\)

= 30 - \(\frac{7}{32}\)

= \(\frac{960}{32}\) - \(\frac{7}{32}\)

= 953/32

Câu b:

71\(\frac{38}{45}\) - (43\(\frac{8}{45}\) - 1\(\frac{17}{57}\))

= 71\(\frac{38}{45}\) - 43\(\frac{8}{45}\) - 1\(\frac{17}{57}\)

= 28\(\frac{30}{45}\) - 1\(\frac{17}{57}\)

= 28\(\frac23\) - 1\(\frac{17}{57}\)

= \(\frac{86}{3}\) - \(\frac{74}{57}\)

= \(\frac{1634}{57}\) - \(\frac{74}{57}\)

= \(\frac{1560}{57}\)

= 520/19

\(bai1:a,\frac{3}{7}\cdot\frac{-5}{9}+\frac{4}{9}\cdot\frac{3}{7}-\frac{3}{7}\cdot\frac{8}{9}\)

\(< =>\frac{-15}{63}+\frac{12}{63}-\frac{24}{63}\)

\(< =>\frac{-15+12-24}{63}\)

\(< =>\frac{-3}{7}\)

\(b,1\frac{13}{15}\cdot0,75-\left(\frac{11}{20}+25\%\right):\frac{7}{5}\)

\(< =>\frac{28}{15}\cdot\frac{3}{4}-\left(\frac{11}{20}+\frac{1}{4}\right):\frac{7}{5}\)

\(< =>\frac{7}{5}-\frac{4}{5}:\frac{7}{5}\)

\(< =>\frac{7}{5}-\frac{4}{7}\)

\(< =>\frac{29}{35}\)

\(bai2:\)

\(a,\frac{-3}{4}\cdot x-\frac{4}{10}=\frac{1}{5}\)

\(< =>\frac{-3}{4}\cdot x=\frac{1}{5}+\frac{4}{10}\)

\(< =>\frac{-3}{4}\cdot x=\frac{3}{5}\)

\(< =>x=\frac{3}{5}:\frac{-3}{4}\)

\(< =>x=\frac{-4}{5}\)

\(b,3\left(x-\frac{1}{3}\right)+\frac{1}{3}x=\frac{1}{19}:\frac{12}{19}\)

\(< =>3\left(x-\frac{1}{3}\right)+\frac{1}{3}x=\frac{1}{12}\)

\(< =>\left[3\left(x-\frac{1}{3}\right)\right]=\frac{1}{12}< =>x-\frac{1}{3}=\frac{1}{12}:3=\frac{1}{36}=>x=\frac{1}{36}+\frac{1}{3}=>x=\frac{13}{36}\)

\(< =>\left[\frac{1}{3}\cdot x\right]=\frac{1}{12}< =>x=\frac{1}{12}:\frac{1}{3}=>x=\frac{1}{4}\)

Bài 1:

a)\(\frac{3}{7}.\frac{-5}{9}+\frac{4}{9}.\frac{3}{7}-\frac{3}{7}.\frac{8}{9}\)                                 b,\(1\frac{13}{15}.0,75-\left(\frac{11}{20}+25\%\right):\frac{7}{5}\)

 \(=\frac{3}{7}.(\frac{-5}{9}+\frac{4}{9}-\frac{8}{9})\)                                       \(=\frac{28}{15}.\frac{3}{4}-\left(\frac{11}{20}+\frac{5}{20}\right):\frac{7}{5}\) 

  \(=\frac{3}{7}.\frac{-9}{9}\)                                                                  \(=\frac{7}{5}-\frac{4}{5}:\frac{7}{5}\)

\(=\frac{-3}{7}\)                                                                           \(=\frac{7}{5}-\frac{4}{7}\)

                                                                                               \(=\frac{29}{35}\)

Bài 2:

a)\(\frac{-3}{4}x-\frac{4}{10}=\frac{1}{5}\)                                               b,\(3\left(x-\frac{1}{3}\right)+\frac{1}{3}x=\frac{1}{19}:\frac{12}{19}\)

  \(\frac{-3}{4}x\)           \(=\frac{1}{5}+\frac{4}{10}\)                                     \(3\left(x-\frac{1}{3}\right)+\frac{1}{3}x=\frac{1}{12}\)

\(\frac{-3}{4}x\)             \(=\frac{3}{5}\)                                            \(\left(x.3-\frac{1}{3}.3\right)+\frac{1}{3}x=\frac{1}{12}\)     

         \(x\)              \(=\frac{3}{5}:\frac{-3}{4}\)                                        \(\left(x.3-1\right)+\frac{1}{3}x=\frac{1}{12}\)                                         

         \(x\)              \(=\frac{4}{-5}\)                                                   \(x.\left(3+\frac{1}{3}\right)-1=\frac{1}{12}\)

                                                                                                             \(x.\left(3+\frac{1}{3}\right)=\frac{1}{12}+1\) 

                                                                                                                          \(x.\frac{10}{3}=\frac{13}{12}\) 

                                                                                                                                    \(x=\frac{13}{12}:\frac{10}{3}\) 

                                                                                                                                     \(x=\frac{13}{40}\)                             

-5/12 . 2/7 + 7/12 . -3/4

= -10/84 + -21/48

= -5/42 + -7/16  

= -40/336 + -147/336

= -187/336

\(\frac{-5}{12}\).\(\frac{2}{7}\)+\(\frac{7}{12}\).\(\frac{-3}{4}\)

=\(\frac{5}{12}\).\(\frac{-2}{7}\)+\(\frac{7}{12}\).\(\frac{-3}{4}\)

=\(\frac{5}{12}\).(\(\frac{-2}{7}\)+\(\frac{-3}{4}\))

\(\frac{5}{12}\).\(\frac{-29}{28}\)

=\(\frac{-145}{336}\)

((nho k cho mink nhe)