a,986280

b,13/8

c,7/6

d,377,16

889972+96308=986280

7/8+3/4=7/8 + 6/8 = 13/8

c)2-5/6 = 7/6

d) 726,83 - 349,67 = 377,16

a, 986280

b, 13/8

c,7/6

d, 377,16

889972+96308  =986380

2-5/6=7/6

7/8+3/4=2

726,83-349,67=375,16

a) 889972 + 96308 = 986280

b) \(\dfrac{5}{6}+\dfrac{7}{12}=\dfrac{10}{12}+\dfrac{7}{12}=\dfrac{17}{12}\)

c) \(3+\dfrac{5}{7}=\dfrac{21}{7}+\dfrac{5}{7}=\dfrac{26}{7}\)

d) 926,83 + 549,67 = 1476,5

a)889972 + 96308=986280

c)3+5/7=21/7+5/7=26/7

b)5/6+7/12=10/12+7/12=17/12

d)926,83+549,67=1476,5

a) 889972 + 96308=986280

b) \(\dfrac{5}{6}\)+\(\dfrac{7}{12}\)=\(\dfrac{10}{12}\)+\(\dfrac{7}{12}\)=\(\dfrac{17}{12}\)

c) 3+\(\dfrac{5}{7}\)=\(\dfrac{21}{7}\)+\(\dfrac{5}{7}\)=\(\dfrac{26}{7}\)

d) 926,83 +549,67=1476,5

1.

a) 889972 + 96306 = 986278

b) 726,83 - 349,67 = 377,16

c) \(\frac{7}{8}+\frac{3}{4}=\frac{13}{8}\)

d)\(2-\frac{5}{6}=\frac{7}{6}\)

7/8+3/4=13/8

889972+96308=986280

\(\frac{7}{8}+\frac{3}{4}=\frac{13}{8}\)

\(889972+96308=986280\)

\(\frac{7}{8}\)+ \(\frac{3}{4}\)= \(\frac{13}{8}\)

889972 + 96308 = 986280

`@` `\text {Ans}`

`\downarrow`

`1,`

`a)`

`-7/25 + (-8)/25`

`= (-7 - 8)/25`

`= -15/25`

`= -3/5`

`b)`

`6/13 + (-15)/39`

`= 18/39 + (-15)/39`

`= (18 - 15)/39`

`= 3/39`

`= 1/13`

`c)`

`5/7 + 4/(-14)`

`= 10/14 + (-4)/14`

`= (10 - 4)/14`

`= 6/14`

`= 3/7`

`d)`

`-8/18 + (-15)/27`

`= -4/9 + (-5)/9`

`= (-4-5)/9`

`= -9/9 = -1`

`2,`

`a)`

`3/5 + (-7)/4`

`= 12/20 + (-35)/20`

`= (12 - 35)/20`

`=-23/20`

`b)`

`(-2) + (-5)/8`

`= (-16)/8 + (-5)/8`

`= (-16 - 5)/8`

`= -21/8`

`c)`

`1/8 + (-5)/9`

`= 9/72 + (-40)/72`

`= (9-40)/72`

`= -31/72`

`d)`

`6/13 + (-14)/39`

`= 18/39 + (-14)/39`

`= (18 - 14)/39`

`= 4/39`

`e)`

`(-18)/24 + 15/21`

`= (-3)/4 + 5/7`

`= (-21)/28 + 20/28`

`= (-21 + 20)/28`

`= -1/28`

\(\dfrac{7}{5}+\dfrac{4}{7}-\dfrac{9}{10}=\dfrac{49-20}{35}-\dfrac{9}{10}=\dfrac{19}{35}-\dfrac{9}{10}=\dfrac{190-315}{350}=\dfrac{-125}{350}\)

\(\dfrac{2}{1}+\dfrac{3}{4}\text{×}\dfrac{8}{5}=\dfrac{8+3}{4}\text{×}\dfrac{8}{5}=\dfrac{11\text{×}8}{4\text{×}5}=\dfrac{88}{20}\)

mấy câu kia áp dụng là dc!

\(a,=\frac{7-1}{1.3.7}+\frac{9-3}{3.7.9}+\frac{13-7}{7.9.13}+\frac{15-9}{9.13.15}\)\(+\frac{19-13}{13.15.19}\)

\(=\frac{1}{1.3}-\frac{1}{3.7}+\frac{1}{3.7}-\frac{1}{7.9}+\frac{1}{7.9}-\frac{1}{9.13}+\frac{1}{9.13}-\frac{1}{13.15}+\frac{1}{13.15}-\frac{1}{15.19}\)

\(=\frac{1}{1.3}-\frac{1}{15.19}=\frac{95}{285}-\frac{1}{285}=\frac{94}{285}\)

\(b,=\frac{1}{6}.\left(\frac{6}{1.3.7}+\frac{6}{3.7.9}+\frac{6}{7.9.13}+\frac{6}{9.13.15}+\frac{6}{13.15.19}\right)\)

làm giống như trên

\(c,=\frac{1}{8}.\left(\frac{1}{1.2.3}+\frac{1}{2.3.4}+\frac{1}{3.4.5}+...+\frac{1}{48.49.50}\right)\)

\(=\frac{1}{16}.\left(\frac{2}{1.2.3}+\frac{2}{2.3.4}+\frac{2}{3.4.5}+...+\frac{2}{48.49.50}\right)\)

\(=\frac{1}{16}.\left(\frac{3-1}{1.2.3}+\frac{4-2}{2.3.4}+\frac{5-3}{3.4.5}+...+\frac{50-48}{48.49.50}\right)\)

\(=\frac{1}{16}.\left(\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-\frac{1}{3.4}+\frac{1}{3.4}-\frac{1}{4.5}+...+\frac{1}{48.49}-\frac{1}{49.50}\right)\)

\(=\frac{1}{16}.\left(\frac{1}{2}-\frac{1}{2450}\right)=\frac{1}{16}.\left(\frac{1225}{2450}-\frac{1}{2450}\right)=\frac{153}{4900}\)

\(d,=\frac{5}{7}.\left(\frac{7}{1.5.8}+\frac{7}{5.8.12}+\frac{7}{8.12.15}+...+\frac{7}{33.36.40}\right)\)

\(=\frac{5}{7}.\left(\frac{8-1}{1.5.8}+\frac{12-5}{5.8.12}+\frac{15-8}{8.12.15}+...+\frac{40-33}{33.36.40}\right)\)

\(=\frac{5}{7}.\left(\frac{1}{1.5}-\frac{1}{5.8}+\frac{1}{5.8}-\frac{1}{8.12}+\frac{1}{8.12}-\frac{1}{12.15}+...+\frac{1}{33.36}-\frac{1}{36.40}\right)\)

\(=\frac{5}{7}.\left(\frac{1}{5}-\frac{1}{1440}\right)=\frac{5}{7}.\left(\frac{288}{1440}-\frac{1}{1440}\right)=\frac{41}{288}\)

P/S: . là nhân nha

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Cái này dễ thế mà ko bít lm

a)|x|-7=-5

|x|=-5+7

|x|=2

=> x= 2 hoặc x=-2

b)12-|x|=5

|x| = 12 - 5

|x| = 7

=> x= 7 hoặc x= -7

c)|x+3|=4

=> x+3=4         hoặc         x+3=-4

      x=4-3                            x=-4-3

      x=1                                x=-7

vậy x=1 hoặc x=-7

d)|x+8|=|-6|

|x+8|=6

=>x+8=6        hoặc         x+8=-6

    x=6-8                            x=-6-8

    x=-2                              x=-14

vậy x=-2 hoặc x=-14

a)|x|-7=-5

/x/     = (-5) + 7

/x/     = 2

=> x = 2 hoặc x = -2

b)12-|x|=5

      /x/ = 12 - 5

     /x/  = 7

=> x = 7 hoặc x = -7

c)|x+3|=4

  x + 3 = 4              hoặc         x + 3 = -4

 x        = 4 - 3                          x      = (-4) - 3

 x        = 1                               x       = -1

d)|x+8|=|-6|

 /x+ 8 / = 6

x + 8   = 6              hoặc              x + 8 = -6

x         = 6-8                                x       = (-6) - 8

x         = -2                                  x       = -14