câu a : 

\(\dfrac{-8}{24}+\dfrac{-4}{12}=\dfrac{-1}{3}+\dfrac{-1}{3}=\dfrac{-2}{3}\)

câu b : 

\(\dfrac{-20}{35}+\dfrac{16}{24}=\dfrac{-4}{7}+\dfrac{2}{3}=\dfrac{2}{21}\)

câu c : 

\(\dfrac{-3}{9}+\dfrac{-6}{15}=\dfrac{-1}{3}+\dfrac{-2}{5}=\dfrac{-11}{15}\)

câu d : 

\(\dfrac{3}{13}-\dfrac{4}{10}=\dfrac{3}{13}-\dfrac{2}{5}=\dfrac{-11}{65}\)

câu e : 

\(\dfrac{5}{17}-\dfrac{9}{15}=\dfrac{5}{17}-\dfrac{3}{5}=\dfrac{-26}{85}\)

câu g : 

\(\dfrac{9}{18}-\dfrac{6}{15}+\dfrac{3}{-9}=\dfrac{9}{18}-\dfrac{6}{15}+\dfrac{-3}{9}\\ =\dfrac{1}{2}-\dfrac{2}{5}+\dfrac{-1}{3}=\dfrac{-7}{30}\)

câu h : 

\(\dfrac{5}{4}-\dfrac{1}{2}+\dfrac{-7}{8}=\dfrac{10}{8}-\dfrac{4}{8}+\dfrac{-7}{8}=\dfrac{-1}{8}\)

giúp với

Ý đề bài bạn có phải là thế này ko?

\(\dfrac{7^{80}}{\left(-13^4\right)}-\dfrac{2^9}{\left(8-8^3\right)}--5^{24}.\left(-10^3+28^{15}\right)^2\)

1x2x3x4x5x6x7x8x9

2x3x4x5x6x7x8x9x10

=1/10

b)1/2*2/3*3/4*4/5*5/6*6/7*7/8*8/9*9/10

=1x2x3x4x5x6x7x8x9

  2x3x4x5x6x7x8x9x10

= 1

  10

a. bằng77

b. bằng 13

lớp 2 đã học cái này rồi à

a. bằng77

b. bằng 13

1) \(373737.73-37.737373\)

\(=37.10101.73-37.73.10101\)

\(=0\)

2) \(19.41414141-41.19191919\)

\(=19.41.1010101-41.19.1010101\)

\(=0\)

3) \(123456.456789456789-456789.123456123456\)

\(=123456.456789.1000001-456789.123456.1000001\)

\(=0\)

4) \(250.12.7\)

\(=250.4.3.7\)

\(=\left(250.4\right).\left(3.7\right)\)

\(=1000.21\)

\(=21000\)

5) \(24.125.9\)

\(=3.8.125.9\)

\(=\left(3.9\right).\left(8.125\right)\)

\(=27.1000\)

\(=27000\)

6) \(125.44.18\)

\(=125.4.11.2.9\)

\(=\left(125.4.2\right).\left(11.9\right)\)

\(=1000.99\)

\(=99000\)

7) \(8.24.6+12.4.52+2.22.24\)

\(=48.24+48.52+48.22\)

\(=48\left(24+52+22\right)\)

\(=48.98\)

\(=48\left(100-2\right)\)

\(=48.100-48.2\)

\(=4800-96\)

\(=4704\)

8) \(18.58.2-9.27.4+12.69.3\)

\(=36.58-36.27+36.69\)

\(=36\left(58-27+69\right)\)

\(=36.100=3600\)

9) \(30.85.3+18.72.5-45.37.2-9.20.10\)

\(=90.85+90.72-90.37-90.20\)

\(=90\left(85+72-37-20\right)\)

\(=90.100=9000\)

99

Tính các tổng sau:

1, S=1-2+3_4+..+25-26

S =-1+3-5+7-...-53+55                       ( có 28 số hạng )

   = (-1+3)+(-5+7)+...+(-53+55)         ( có 28:2=14 nhóm )

   = 2+2+...+2

    = 2 . 14

     = 28

Á nhầm rùi xl bn nha

3 

S =-1+3-5+7-...-53+55     ( có 28 số hạng )

   = (-1+3)+(-5+7)+...+(-53+55)      ( có 28:2=14 nhóm )

   = 2+2+...+2

    = 2 . 14

     = 28

mn ơi e vít nhầm là tính rồi rút gọn mn sửa lại là rút gọn rùi tính

a: =2/5+3/5=1

b: =1/3+5/6=2/6+5/6=7/6

c: =7/8+5/8=12/8=3/2

d: =2/3+2/10

=20/30+6/30

=26/30=13/15

e: =1/2+1/3

=3/6+2/6

=5/6

f: =2/7+1/6

=12/42+7/42

=19/42

a) 3/5x7/8:10/9=21/40:10/9=189/400

b) 3 2/7x2 1/4:1 2/5=23/7x9/4:7/5=207/28:7/5=1035/196

c) 6/9+24/15+12/9+6/15=34/15+12/9+6/15=18/5+6/15=4

d) 3 2/9-( 1 5/8+1 2/9 )=29/9-(13/8+11/9)=29/9-205/72=3/8

tinh

a)  3/5 x 7/8 : 10/9

b) 3 2/7 x 2 1/4 : 1 2/5

c) 6/9 + 24/15 + 12/9 + 6/15