a) 12/17 : 17/12 + 5/7 : 17/12

= (12/17 + 5/7) : 17/12

= 1 : 17/12

= 12/17

Bài làm

Cách 1 :\(\frac{12}{17}:\frac{17}{12}+\frac{5}{7}:\frac{17}{12}\)

= \(\frac{12}{17}.\frac{12}{17}+\frac{5}{7}.\frac{12}{17}\)

= \(\frac{12}{17}.\left(\frac{12}{17}+\frac{5}{7}\right)\)

= \(\frac{12}{17}.\frac{169}{119}\)

= \(\frac{2028}{2023}\)

Cách 2 : \(\frac{12}{17}:\frac{17}{12}+\frac{5}{7}:\frac{17}{12}\)

= \(\frac{144}{289}+\frac{60}{119}\)

= \(\frac{2028}{2023}\)

1. 12/17:17/12+5/7:17/12=144/289+60/119=2028/2023

2.12/17:17/12+5/7:17/12=(12/17+5/7):17/12=169/119:17/12=2028/2023

Chúc bn học giỏi

kb nhé châm

a) 2/5+3/4=23/20

7/12-2/7+1/12=8//21

 12/17-5/17-4/17=3/17

b) 675,39+342,14=1017,53

563,87+403,13-328,35=638,65

a)            2/5+3/4

           =8/20+15/20

           =21/20

             7/12-2/7+1/12

            =7/12+1/12-2/7

             =1/4-2/7

              =7/28-8/28

              =-1/28

                 12/17-5/17-4/17

               =12/17-9/17

               =3/17

b)              675,39+342,14

               =       1017,53

                   563,87+403,13-328,35

                =       967-328,35

                 =  638,65

\(a,0,5x-\frac{2}{3}x=\frac{7}{12}\Rightarrow\frac{1}{2}x-\frac{2}{3}x=\frac{7}{12}\)

\(\Rightarrow x\left(\frac{1}{2}-\frac{2}{3}\right)=\frac{7}{12}\Rightarrow x\cdot\left(\frac{3}{6}-\frac{4}{6}\right)=\frac{7}{12}\)

\(\Rightarrow x\cdot\left(-1\right)=\frac{7}{12}\Rightarrow x=\frac{7}{12}:\left(-1\right)=\frac{7}{-12}\)

\(c,\frac{\left(x-5\right)}{12}\cdot\frac{9}{29}=\frac{-6}{29}\Rightarrow\frac{\left(x-5\right)}{12}=\frac{-6}{29}:\frac{9}{26}\)

\(\frac{\Rightarrow\left(x-5\right)}{12}=\frac{-6}{9}=\frac{-2}{3}\Rightarrow x-5=-\frac{2}{3}\cdot12\)

\(\Rightarrow x-5=\frac{-24}{3}=-8\Rightarrow x=-8+5=-3\)

\(a,0,5x-\frac{2}{3}x=\frac{7}{12}\)

\(\Rightarrow\frac{1}{2}x-\frac{2}{3}x=\frac{7}{12}\)

\(\Rightarrow-\frac{1}{6}x=\frac{7}{12}\)

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

\(c,\frac{x-5}{12}\cdot\frac{9}{29}=-\frac{6}{29}\)

\(\Rightarrow\frac{x-5}{12}=-\frac{2}{3}\)

\(\Rightarrow x-5=12.\left(-\frac{2}{3}\right)\)

\(\Rightarrow x-5=-8\)

\(\Rightarrow x=-3\)

b)\(\frac{-8}{17}+\frac{5}{17}< \frac{x}{17}< \frac{-6}{17}+\frac{9}{17}\)\(\left(x\in Z\right)\)

\(\Rightarrow\frac{-3}{17}< \frac{x}{17}< \frac{3}{17}\)

\(\Rightarrow-3< x< 3\)

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

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

a) (-12) + 25 + 75 + 12 = (-12) + 12 + 25 + 75 = 0 +100 = 100.

b) 60 +12 + (-17) + (-43) = 60 + [(-47) + (-43)] +12.

c) (-2) + (-87) + (-18) + 87 = [(-2) + (-18)] + [(-87) + 87].

d) (-1)+(-2) + 36 + (-17) = 36+[(-1) + (-2) + (-17)].

a, (-12) + 25 + 75 + 12

= [ (-12) + 12] + (25 + 75)

= 0 + 100

= 100

b, 60 + 12 + (-17) + (-43)

= -(17 + 43) + 60 + 12

= - 60 + 60  + 12

= 0 + 12

= 12

Chọn B

a,(-17)+5+8+17=[(-17)+17]+5+8=0+13=13

b. 30+12+(-20)+(-12)=[12+(-12)]+30+(-20)=0+10=10

Nho k minh nha

a, (-17) + 5 + 8 + 17

   = -12 + 8 + 17

   = -4 + 17

   = 17 - 4

   = 13

b, 30 + 12 + (-20) + (-12)

   = 42 + (-20) + (-12) 

   = 42 - 20 - 12

   = (42 - 12) - 20

   = 30 - 20

   = 10

\(A.4-\left(12-17\right)=17-\left(x-4+15\right)\)

\(\Leftrightarrow4-\left(-5\right)=17-\left(x+11\right)\)

\(\Leftrightarrow9=17-x-11\)

\(\Leftrightarrow6-x=9\)

\(\Leftrightarrow x=6-9\)

\(\Leftrightarrow x=-3\)

\(B.14-\left(12-x\right)=4-\left(15-13\right)\)

\(\Leftrightarrow14-12+x=4-2\)

\(\Leftrightarrow2+x=2\)

\(\Leftrightarrow x=2-2\)

\(\Leftrightarrow x=0\)

a) 2/5 + 3/4 =8/20 + 15/20 = 23/20

7/12 - 2/7 + 1/12 = (7/12 + 1/12) - 2/7 = 8/12 - 2/7 = 2/3 - 2/7 = 14/21 - 6/21 =8/21

12/17 - 5/17 - 4/17 = 7/17 - 4/17 = 3/17

b) 675,39 + 342,14 = 1017,53 

 563,87 + 403,13 - 328,35 = 967 - 328,35 = 638,65

 Chúc bạn học tốt

a)12/17+19/17+8/17=(12/17+8/17)+19/17=20/17+19/17=39/17

b)2/5+7/12+13/12=2/5+(7/12+13/12)=2/5+5/3=31/15

~HT~

k cho mình nha

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