a, \(4\cdot21\cdot25\)

\(=\left(4\cdot25\right)\cdot21=100\cdot21=2100\)

b, \(173\cdot12-12\cdot73\)

\(=12\left(173-73\right)=12\cdot100=1200\)

2100, 150672

4.21.25

= 4.25.21

=100.21

=2100

173.12-12.73

= 12. ( 173-73)

=12.100

=1200

~LucMIlk~

giúp mik nha

888.888.888.889

A = 1 + 1/110 + 1 + 1/90 + ... + 1  + 1 /2 

A = 10 + 1/1.2+ 1 /2.3 + ... + 1/9.10 + 1/10.11

A = 10 + 1/1 - 1/2 + 1 /2 - 1/3 + ... + 1/9 - 1/10 + 1/10 - 1/11

A = 10 + 1/1 - 1/11

A = 10 + 10/11

A = 120/11

A = \(\frac{111}{110}+\frac{91}{90}+\frac{73}{72}+...+\frac{13}{12}+\frac{7}{6}+\frac{3}{2}\)

A = \(\left(\frac{1}{2}+1\right)+\left(\frac{1}{6}+1\right)+\left(\frac{1}{12}+1\right)+....+\left(\frac{1}{110}+1\right)\)

A = (1 + 1 + 1 +...+ 1) + \(\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+...+\frac{1}{110}\right)\)

A = 10 + \(\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{10.11}\right)\)

A = \(10+\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{10}-\frac{1}{11}\right)\)

A = \(10+\left(1-\frac{1}{11}\right)\)

A = \(10+\frac{10}{11}\)

A = \(\frac{120}{11}\)

hello bạn 

Tính nhanh : 

73.(-12)+(-73).88

= 73.(-12) +73.(-88)

= 73.(-12 - 88)

= 73.(-100)

= -7300

k cho mk nha

a) 91 - x = 90

          x = 91 - 90

          x = 1

b) x - 73.21 = 73.26

    x = 73.26 + 73.21

    x = 73.(26 + 21)

    x = 73.47

    x = 3431

c) 6.(x + 11) = 0

    x + 11 = 0 : 6

    x + 11 = 0

   x = 0 - 11

   x = -11

d) 2x - 12 - x = 9

   => 2x - (12 + 9) = x

   => (2 - 1)x = 21

   => x = 21

a)x=1

b)x=3431

c)x=-11

d)x=21

91-x =90

x =91 -90

x =1

(-235)-173-(-73)+|-235|

= -235-173+73+235

= (235-235) - (173-73)

= 0 - 100

= -100

\(=\left(-235\right)-173\)\(+73+235\)

\(=\left[\left(-235\right)+235\right]\)\(+\left(-173+73\right)\)

\(=0+\left(-100\right)=-100\)

(-235) - 173 - (-73) + |-235|

= (-235) - 173 + 73 + 235

= (-235 + 235) - (173 - 73)

= 0 - 100

= -100

13700

\(=13700\)

giải chi tiết nha 

b: \(=12\left(35\cdot173+27\right)\)

\(=12\cdot6082=72984\)

có j đó sai