18+(-6)+23+(-7)-5=[18+(-6)]+23+[(-7)-5]

                             =12+23+(-12)=23

\

bn giúp mk câu còn lại nữa nha

Trả lời:

a, 18 + (-6) + 23 + (-7) - 5

= 12 + 23 + [ (-7) - 5 ]

= 12 + 23 + (-12)

= 23

b,-25 + 34 - (16 - 45)

= -25 + 34 - 16 + 45

= (-25 + 45) + (34 - 16)

= 20 + 18

= 38

c, [ 4 - (-21) + 7 ] - 5

= 4 + 21 + 7 - 5

= 25 - 5 + 7

= 20 + 7

= 27

Hok tốt!

-,- -,-                   rốối quá

(Vẫn rút gọn hở ?)

4. \(\frac{64^3.36^2}{16^4.18^5}=\frac{\left(2^6\right)^3.\left(2^2.3^2\right)^2}{\left(2^4\right)^4.\left(2.3^2\right)^5}=\frac{2^{18}.\left(2^2\right)^2.\left(3^2\right)^2}{2^{16}.2^5.\left(3^2\right)^5}\)

   \(=\frac{2^{18}.2^4.3^4}{2^{16}.2^5.3^{10}}=\frac{2^{22}.3^4}{2^{21}.3^{10}}=\frac{2}{3^6}\)

5. \(\frac{34^{18}.68^{24}}{17^{30}.2^{16}}=\frac{\left(2.17\right)^{18}.\left(2^2.17\right)^{24}}{17^{30}.2^{16}}=\frac{2^{18}.17^{18}.\left(2^2\right)^{24}.17^{24}}{17^{30}.2^{16}}\)

\(=\frac{2^{18}.17^{18}.2^{48}.17^{24}}{17^{30}.2^{16}}=\) \(\frac{2^{66}.17^{42}}{17^{30}.2^{16}}=2^{50}.17^{12}\)

1)` 2/9 + -3/4 + 5/30= (40+(-135) + 30 )/180 = -65/180 = -13/36`

2) `-7/12 - 11/18=(-21)/36 - 22/36 = -43/36 `

3) `7/8 - (-5)/16=14/16- (-5)/16 = 19/16 `

4) `3/8 - (-9)/10 - 5/16= (30- (-72) -25)/80=77/80`

1)\(\dfrac{2}{9}+\dfrac{-3}{4}+\dfrac{5}{30}\)

\(=\dfrac{2.20}{9.20}+\dfrac{-3.45}{4.45}+\dfrac{5.6}{30.6}\)

\(=\dfrac{40}{180}+\dfrac{-135}{180}+\dfrac{30}{180}\)

\(=\dfrac{40+\left(-135\right)+30}{180}\)

\(=\dfrac{-65}{180}\)

\(=\dfrac{-13}{36}\)

2)\(\dfrac{-7}{12}-\dfrac{11}{18}\)

\(=\dfrac{-7.3}{12.3}-\dfrac{11.2}{18.2}\)

\(=\dfrac{-21}{36}-\dfrac{22}{36}\)

\(=\dfrac{-21-22}{36}\)

\(=\dfrac{-43}{36}\)

3)\(\dfrac{7}{8}-\dfrac{-5}{16}\)

\(=\dfrac{7.2}{8.2}-\dfrac{-5}{16}\)

\(=\dfrac{14}{16}-\dfrac{-5}{16}\)

\(=\dfrac{14-\left(-5\right)}{16}\)

\(=\dfrac{19}{16}\)

4)\(\dfrac{3}{8}-\dfrac{-9}{10}-\dfrac{5}{16}\)

\(=\dfrac{3.10}{8.10}-\dfrac{-9.8}{10.8}-\dfrac{5.5}{16.5}\)

\(=\dfrac{30}{80}-\dfrac{-72}{80}-\dfrac{25}{80}\)

\(=\dfrac{30-\left(-72\right)-25}{80}\)

\(=\dfrac{77}{80}\)

8006

423 x 18 + 423 + 16 - 423 : 9 = 8006

8006

\(423\times18+423\times16-423:9\\ =423\times18+423\times16-423\times\dfrac{1}{9}\\ =423\times\left(18+16-\dfrac{1}{9}\right)\\ =423\times\dfrac{350}{9}\\ =14335\)

423×18+423×16−423:9=423×18+423×16−423×19=423×(18+16−19)=423×3509=14335

\(\frac{-1}{39}+\frac{-1}{52}=\frac{-7}{156}\)

\(\frac{-6}{9}+\frac{12}{16}=\frac{-2}{3}+\frac{3}{4}=\frac{1}{12}\)

\(\frac{-2}{5}-\frac{-3}{11}-\frac{34}{37}-\frac{74}{-85}=\frac{-1215}{6919}\)

\(\frac{-5}{9}:\frac{-7}{18}=\frac{-5}{9}.\frac{-18}{7}=\frac{10}{7}\)

bấm mt

-1/39 + -1/52 = -7/156

-6/9 + -12/16 = -17/12

-2/5 - - 3/11 [ (-) + ( -) = +] = -2/5 + 3/11 = -7/55

-34/37 - 74/ -85 = -152/3145

-5/9 : -7/18 = 10/7

 -7/156

-17/12

-7/55

-152/3145

10/7

Quy đồng rồi tính là ra ngay mà

Đọc dòng cuối thì thấy ko muốn giúp

mình chịu

Áp dụng tính chất của dãy tỉ số bằng nhau, ta được:

\(\dfrac{a}{12}=\dfrac{b}{20}=\dfrac{c}{25}=\dfrac{a-b+c}{12-20+25}=\dfrac{34}{17}=2\)

Do đó: a=24; b=40; c=50