Lời giải:
Gọi phân số trên là $A$. Ta có:

$A=\frac{12,48:6,48\times 2\times 8\times 6,25\times 3,25\times 4\times 4\times 2}{3,12\times 21,6\times 1,25\times 2,6\times 4\times 4\times 10\times 10}$

$=\frac{12,48:6,48\times (2\times 6,25)\times (8\times 3,25)\times 2}{3,12\times 21,6\times (1,25\times 10)\times (2,6\times 10)}$

$=\frac{12,48:6,48\times 12,5\times 26\times 2}{3,12\times 21,6\times 12,5\times 26}$

$=\frac{12,48:6,48\times 2}{3,12\times 21,6}=\frac{125}{2187}$

\(\frac{12,48:0,5x6,25x4x2}{2x3,12x1,25:0,25x10}=\frac{4x3,12x2x5x1,25x4x2}{2x3,12x1,25x4x2x5}=4\)

hôm nay tôi vừa làm xong

chịu thôi

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hỏi chị tuyển đi

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\(A=\frac{1.25.10:0,25.24,4.2}{6,1.2.6,25.4:0,5}.\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right)\times...\times\left(1-\frac{1}{19}\right).\left(1-\frac{1}{20}\right)\)

\(A=\frac{50.48,8}{6,1.100}\times\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times...\times\frac{18}{19}\times\frac{19}{20}\)

\(A=\frac{4}{1}\times\frac{1}{1}\times\frac{1}{20}\)

\(A=\frac{4}{20}\)

Ta có: \(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}+\frac{1}{128}\)

 = \(\frac{1}{2}+\left(\frac{1}{2}-\frac{1}{4}\right)+\left(\frac{1}{4}-\frac{1}{8}\right)+....+\left(\frac{1}{64}-\frac{1}{128}\right)\)

=\(\frac{1}{2}+\frac{1}{2}-\frac{1}{128}\)

\(=1-\frac{1}{128}=\frac{127}{128}\)

MẤY CÂU KHÁC THÌ SAO?

= \(\frac{1x1x1}{1x2x4}x\frac{2.2.1}{1.1.2.2}=\frac{1}{8}.1=\frac{1}{8}\)

=1X2X3/1X2X3X4X2= 1/8                 =3X2X2X2X5/3X2X2X5X2= 1/1

=1/8X1/1=1/8

Tính giá trị biểu thức:

\(\frac{1\times2\times3}{1\times6\times8}\times\frac{6\times4\times5}{3\times2\times2\times10}\)   

\(=\frac{1}{8}\times1=\frac{1}{8}\)

Ủng hộ nha! :) 

\(1\frac{13}{15}\cdot3\cdot(0,5)^2\cdot3+\left[\frac{8}{15}-1\frac{19}{60}:1\frac{23}{24}\right]\)

\(=\frac{28}{15}\cdot3\cdot0,5\cdot0,5\cdot3+\left[\frac{8}{15}-\frac{79}{60}:\frac{47}{24}\right]\)

\(=\frac{28}{5}\cdot0,25\cdot3+\left[\frac{32}{60}-\frac{79}{60}\cdot\frac{24}{47}\right]\)

\(=\frac{28}{5}\cdot\frac{25}{100}\cdot3+\left[\frac{32}{60}-\frac{158}{235}\right]\)

\(=\frac{28}{5}\cdot\frac{1}{4}\cdot3+\frac{-98}{705}=\frac{7}{5}\cdot1\cdot3+\frac{-98}{705}\)

Đến đây là tính dễ rồi :v

\((-3,2)\cdot\frac{-15}{64}+\left[0,8-2\frac{4}{15}\right]:1\frac{23}{24}\)

\(=\frac{-32}{10}\cdot\frac{-15}{64}+\left[\frac{8}{10}-\frac{34}{15}\right]:\frac{47}{24}\)

\(=\frac{-32\cdot(-15)}{10\cdot64}+\left[\frac{4}{5}-\frac{34}{15}\right]:\frac{47}{24}\)

\(=\frac{-1\cdot(-3)}{2\cdot2}+\frac{4\cdot3-34}{15}:\frac{47}{24}\)

\(=\frac{3}{4}+\frac{-22}{15}:\frac{47}{24}\)

\(=\frac{3}{4}+\frac{-517}{180}=\frac{-191}{90}\)

Bài 2 : \(\frac{2\cdot(-13)\cdot9\cdot10}{(-3)\cdot4\cdot(-5)\cdot26}=\frac{1\cdot(-1)\cdot3\cdot2}{(-1)\cdot2\cdot(-1)\cdot2}=\frac{1\cdot3}{-1\cdot2}=\frac{3}{-2}=\frac{-3}{2}\)

\(\frac{15\cdot8+15\cdot4}{12\cdot3}=\frac{15\cdot(8+4)}{12\cdot3}=\frac{15\cdot12}{12\cdot3}=\frac{15}{3}=5\)

a)1.2.3.4...9-1.2.3.4...8-1.2.3.4...8.8

=1.2.3.4...8(9-1-8)

=1.2.3.4...8.0

=0

b)(3.4.2¹⁶)²/11.12³.4¹¹-16⁹=(3.2².2¹⁶)²/11.2¹³.2²²-2³⁶=3².2⁴.2³²/11.2³⁵-2³⁶=3².2²⁶/2³⁵.(11-2)

=3².2³⁶/2³⁵.9=3².2³⁶/2³⁵.3²=2

c)70.(131313/565656+131313/727272+131313/909090

=70.(13/56+13/72+13/90)

=70.39/70=39

d)1/4.9+1/9.14+1/14.19+...+1/64.69

=4/4.9.4+4/9.4.14+4/14.19.4+...+4/64.69.4.

=1/4.(4/4.9+4/9.14+4/14.19+...+4/64.69)

=1/4.(1/4-1/9+1/9-1/14+1/14-1/19+...+1/64-1/69)

=1/4.(1/4-1/69)

=1/4.65/276=65/1104

~~~~~~~~Chúc bạn học giỏi nhé !~~~~~~~~

nhìu thế này sao mà làm nổi

d)\(\frac{1}{3}\times\left(\frac{1}{4}-\frac{1}{9}+\frac{1}{9}-\frac{1}{14}+...+\frac{1}{64}-\frac{1}{69}\right)\)

\(\frac{1}{3}\times\left(\frac{1}{4}-\frac{1}{69}\right)\)

\(\frac{1}{3}\times\frac{65}{276}\)