a)\(-\dfrac{2}{5}.\dfrac{4}{7}+\dfrac{-3}{5}.\dfrac{2}{7}+\dfrac{-3}{5}\) 

=\(-\dfrac{2}{5}.\dfrac{4}{7}+\dfrac{3}{7}.\dfrac{-2}{5}+\dfrac{-3}{5}\)

=\(-\dfrac{2}{5}.\left(\dfrac{4}{7}+\dfrac{3}{7}\right)+\dfrac{-3}{5}\) 

=\(\dfrac{-2}{5}.1+\dfrac{-3}{5}\) 

=\(-\dfrac{2}{5}+\dfrac{-3}{5}\) 

=\(-\dfrac{5}{5}\) = -1

\(\dfrac{5}{9}.\dfrac{14}{17}+\dfrac{1}{17}.\dfrac{5}{9}+\dfrac{2}{9}+\dfrac{5}{12}\)

=\(\dfrac{5}{9}.\left(\dfrac{14}{17}+\dfrac{1}{17}\right)+\dfrac{2}{9}+\dfrac{5}{12}\) 

=\(\dfrac{5}{9}.\dfrac{15}{17}+\dfrac{2}{9}+\dfrac{5}{12}\) 

=\(\dfrac{25}{51}+\dfrac{2}{9}+\dfrac{5}{12}\)

=\(\dfrac{691}{612}\)

\(-\dfrac{4}{25}:\dfrac{11}{79}+\dfrac{15}{11}:\dfrac{25}{79}\)

=\(-\dfrac{4}{25}.\dfrac{79}{11}+\dfrac{15}{11}.\dfrac{79}{25}\)

=\(-\dfrac{4}{25}.\dfrac{79}{11}+\dfrac{15}{25}.\dfrac{79}{11}\) 

=\(\left(-\dfrac{4}{25}+\dfrac{15}{25}\right).\dfrac{79}{11}\)

=\(\dfrac{11}{25}.\dfrac{79}{11}\) 

=\(\dfrac{79}{25}\)

a: =-15/24-18/24+60/24

=27/24=9/8

b: =6/12-9/12-10/12-7/12=-20/12=-5/3

c: =17/2+3/7-5/3=305/42

c: =-3-2/3-10/9-25/3-5/6

=-10-19/9-5/6

=-180/18-38/18-15/18=-233/18

a)\(1-2+3-4+5-6+7-8+8-9+9-10\)

=\(\left(1-2\right)+\left(3-4\right)+\left(5-6\right)+\left(7-8\right)+\left(8-9\right)+\left(9-10\right)\)

\(=\left(-1\right)+\left(-1\right)+\left(-1\right)+\left(-1\right)+\left(-1\right)+\left(-1\right)\)

\(=\left(-1\right).6\)

\(=-6\)

b)\(1-2+3-4+...+99-100\)

\(=\left(1-2\right)+\left(3-4\right)+...+\left(99-100\right)\)}\(\left[\left(100-1\right):1+1\right]:2=50\)(cặp)

\(=\left(-1\right)+\left(-1\right)+\left(-1\right)+...+\left(-1\right)\)} 50 số (-1)

\(=\left(-1\right).50\)

\(=-50\)

c)\(1-3+5-7+9-11+13-15\)

\(=\left(1-3\right)+\left(5-7\right)+\left(9-11\right)+\left(13-15\right)\)

\(=\left(-2\right)+\left(-2\right)+\left(-2\right)+\left(-2\right)\)

\(=\left(-2\right).4\)

\(=-8\)

d)\(1-3+5-7+...-99+101\) (Đối với bài này, có vẻ đề sai, mình đã sửa lại rồi

\(=\left(1-3\right)+\left(5-7\right)+...+\left(97-99\right)+101\) } \(\left[\left(99-1\right):2+1\right]:2=25\)(cặp)

\(=\left(-2\right)+\left(-2\right)+\left(-2\right)+...+\left(-2\right)\) } 25 số (-2)

\(=\left(-2\right).25\)

\(=-50\)

e)\(-1-2-3-4-...-99-100\)

\(=\left(-1\right)+\left(-2\right)+\left(-3\right)+...+\left(-99\right)+\left(-100\right)\)

\(=\left[\left(-1\right)+\left(-100\right)\right]+\left[\left(-2\right)+\left(-99\right)\right]+...+\left[\left(-51\right)+\left(-50\right)\right]\) } \(\left[\left(100-1\right):1+1\right]:2=50\)(cặp) (phần này của đề bài, không thay được như (-100) hoặc (-1))

\(=\left(-100\right)+\left(-100\right)+\left(-100\right)+...+\left(-100\right)\)} 50 số (-100)

\(=\left(-100\right).50\)

\(=-5000\)

a, -5

b, -50

c, -8

d, -50

e, -5050

cách làm nữa nha

Bài 3:
a) 11 - (15 + 11) = x - (25 - 9)
=> 11 - 15 - 11 = x - 25 + 9
=> x = 9 - 25 + 15
=> x =       -1
b) 2 - x = 17 - (-5)
=> 2 - x = 17 + 5
=>    -x = 17 + 5 - 2
=>    -x = 20
=>     x = -20
c) x - 12 = (-9) - 15
=> x - 12 = -9 - 15
=> x        = -9 - 15 + 12
=> x        =        -12
d) IxI - 7 = 9
=> IxI = 9 + 7
=> IxI = 16
=> x = 16      hay     x = -16
e) 9 - 25 = (7 - x) - (25 + 7)
=> 9 - 25 = 7 - x - 25 - 7
=>  x = 7 - 7 - 25 + 25 - 9
=>  x = -9

Bài 4:
a) 25 . 46 + 54 . 25
= 25(46 + 54)
= 25.100
= 2500
b) 1200 : 25
= (25.48) : 25
= 25:25 . 48
=     1.48
=        48
c) 1356 - 998
= 1356 + 2 - 998 - 2
= 1358 - 1000
=        358
d) 117 + 57 - 17
=  117 - 17 + 57
=       100 + 57
=         157

Bài 5:
a) 3⁴ . 3¹⁵
= 3^{4 + 15}
= 3¹⁹
b) 8⁸ : 8⁸
= 8^{8 - 8}
= 8⁰
= 1
c) 100 - [120 - (15 - 5)² ]
=  100 - (120 - 10²⁾
=  100 - (120 - 100)
=  100 - 120 + 100
=            80

Bài 3 : 

a, 11 - ( 15 + 11 ) = x - ( 25 - 9 )

               11 - 26 = x - 16 

                   - 15 = x - 16 

                        x = - 15 + 16 

                        x = 1

b, 2 - x = 17 - ( - 5 )

    2 - x = 22

         x = 2 - 22 

         x = - 20 

c, x - 12 = - 9 - 15 

    x - 12 = - 24 

            x = - 24 + 12 

            x = - 12 

d, | x | - 7 = 9 

    | x | = 9 + 7 

     | x | = 16

     x = 16 hoặc - 16

e, 9 - 25 = ( 7 - x ) - ( 25 + 7 )

      - 16 = 7 - x - 32

        x = 7 - 32 + 16 

        x = - 9

Bài 4 : 

25 x 46 + 54 x 25 

= 25 x ( 46 + 54 )

= 25 x 100

= 2500

b, 1200 : 25

= 12 x 100 : 25 

= 12 x 4 

= 48 

c, 1356 - 998

= 358

d, 117 + 57 - 17 

= ( 117 - 17 ) + 57 

= 100 + 57 

= 157 

Bài 5 :

a, 3^4 . 3^15 

= 3^19

b, 8^8 : 8^8 

= 1 

c, 100 - [ 120 - ( 15 - 5 )^2 ]

= 100 - ( 120 - 100 )

= 100 - 20 = 80

bai 4 : a) = 2500

b)=48

c)=157

bai 5 : a)= 1162261467

b)=1

c)= 80

a: =-1+17/20=-3/20

b: =(28/60-33/60)*(-25/3)

=(-1/12)*(-25/3)=1/12*25/3=25/36

c: \(=\dfrac{1}{3}\cdot\dfrac{1}{3}=\dfrac{1}{9}\)

a)=\(\frac{-2.4}{5.7}+\frac{-3.2}{5.7}+\frac{-3}{5}\)

=\(\frac{-2.4}{5.7}+\frac{-2.3}{5.7}+\frac{-3}{5}\)

=\(\frac{-2}{5}\left(\frac{4+3}{7}\right)+\frac{-3}{5}\)

=\(\frac{-2}{5}.1+\frac{-3}{5}\)

=-1

b)

Giúp mình các câu khác với ngo vinh thien 

please!!