a) 5+(-2)+(18-23)+2

  =5+(18-23)+[(-2)+2]

  =5+  (-5)   +     0

  =           0

b)|-6|:(-3)-43+(-2)².11

   =6:(-3)-43+4.11

   =  -2  -43+  44

   =    -45   + 44

   =         -1

B = ( \(\dfrac{5}{7}.0,6:3\dfrac{1}{2}\)) . ( 40% - 1,4) . \(\left(-2\right)^3\)

= (\(\dfrac{5}{7}.\dfrac{3}{5}\): \(\dfrac{7}{2}\)) . ( \(\dfrac{2}{5}-\dfrac{7}{5}\)) . (-8)

= (\(\dfrac{15}{35}:\dfrac{7}{2}\)) . \(\dfrac{-5}{5}\) . ( -8)

= (\(\dfrac{3}{7}.\dfrac{2}{7}\)) . (-1) . (-8)

= \(\dfrac{6}{49}\) . (-1) . (-8)

= \(\dfrac{-6}{49}\) . (-8)

= \(\dfrac{48}{49}\)

Vậy: B =\(\dfrac{48}{49}\)

Nhớ tick nha

B=(\(\dfrac{3}{7}.\dfrac{2}{7}\)).(\(\dfrac{4}{10}-\dfrac{14}{10}\)).(-8)

B=\(\dfrac{3}{7}.\left(-1\right)\left(-8\right)\)

B=\(\dfrac{24}{7}\)

a ) \(\left(3x^2-4x+5\right)\left(2x^2-4\right)-2x\left(3x^3-4x^2+8\right)\)

\(=\left(3x^2-4x+5\right).2x^2-4\left(3x^2-4x+5\right)-6x^4+8x^3-16x\)

\(=6x^4-8x^3+10x^2-12x^2+16x-20-6x^4+8x^3-16x\)

\(=\left(6x^4-6x^4\right)+\left(8x^3-8x^3\right)-\left(12x^2-10x^2\right)+\left(16x-16x\right)-20\)

\(=-2x^2-20\)

b ) \(\left(1-3x+x^2\right)\left(2-4x\right)+2x\left(2x^2+5\right)\)

\(=2\left(1-3x+x^2\right)-4x\left(1-3x+x^2\right)+4x^3+10x\)

\(=2-6x+2x^2-4x+12x^2-4x^3+4x^3+10x\)

\(=\left(4x^3-4x^3\right)+\left(12x^2+2x^2\right)+\left(10x-6x-4x\right)+2\)

\(=14x^2+2\)

a)187 + [923 - (923 + 887)]

= 187 + [923 - 923 - 887]

= 187 + 923 - 923 - 887

= 187 + 0 - 887

= 187 - 887

= -700

b)39 . 187 + 30² - 78 . 39

= 39 . 187 + 900 - 78 . 39

= 39 . (187 - 78) + 900

= 39 . 109 + 900

= 4251 + 900

= 5151

a, 187+[923-(923+887)]

=187+[923-923-887]

=187-887

=-700

b, 39.187+30²-78.39

=39.(187-78)+900

=39.109+900

=4251+900

=5151

Câu b bạn xem lại đầu bài là 78 hay 87 nha. Là 87 sẽ đúng hơn đó.

a: \(=205-\left[1200-\left(16-6\right)^3\right]:140\)

\(=205-\left[1200-10^3\right]:140\)

\(=205-\dfrac{200}{140}=205-\dfrac{10}{7}=\dfrac{1425}{7}\)

b: \(=\left[25-4\cdot3+9\cdot4+16\right]:5\)

\(=\left(25-12+36+16\right):5=\dfrac{65}{5}=13\)

a)

\(\left[\frac{3}{8}+\frac{-3}{4}+\frac{7}{12}\right]:\frac{5}{6}+\frac{1}{2}\)

=\(\left[\frac{9}{24}+\frac{-18}{24}+\frac{14}{24}\right]:\frac{5}{6}+\frac{1}{2}\)

=\(\frac{5}{24}:\frac{5}{6}+\frac{1}{2}\)

=\(\frac{5}{24}.\frac{6}{5}+\frac{1}{2}\)

=\(\frac{1}{4}+\frac{1}{2}=\frac{1}{4}+\frac{2}{4}=\frac{3}{4}\)

tk ủng hộ mk nha ạ!!!!!!!!!!!!!

\(\left(\frac{3}{8}+\frac{-3}{4}+\frac{7}{12}\right):\frac{5}{6}+\frac{1}{2}\)

\(=\left(\frac{-3}{8}+\frac{7}{12}\right):\frac{5}{6}+\frac{1}{2}\)

\(=\frac{5}{24}:\frac{5}{6}+\frac{1}{2}\)

\(=\frac{1}{4}+\frac{1}{2}\)

\(=\frac{3}{4}\)

3/4 nha 

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mk nha

{[( 10 * 2 * 3 ) * 5 ] + 2 - 2 * 6 } + ( 4 * 5 ) ^ 2

= [ ( 60 * 5 ) + 2 - 12 ] + 20^2

= [ 300 + ( -10 )] + 400

= 290 + 400

= 690