(2525/3737-171717/191919+19/21) x (1/6+1/4-5/12)

=(25/37-17/19+19/21) x 0

=0

Có: \(\dfrac{5454}{5757}-\dfrac{171717}{191919}.\dfrac{3}{4}+\dfrac{1}{4}:x=\dfrac{2}{5}\)

=> \(\dfrac{54.101}{57.101}-\dfrac{17.10101}{19.10101}.\dfrac{3}{4}+\dfrac{1}{4}:x=\dfrac{2}{5}\)

=> \(\dfrac{18}{19}-\dfrac{17}{19}.\dfrac{3}{4}+\dfrac{1}{4}:x=\dfrac{2}{5}\)

=> \(\dfrac{21}{76}+\dfrac{1}{4}:x=\dfrac{2}{5}\)

=> \(\dfrac{1}{4}:x=\dfrac{47}{380}\)

=> x = \(\dfrac{95}{47}\)

=>18/19-17/19*3/4+1/4:x=2/5

=>1/4:x=2/5-18/19+17/19*3/4=47/380

=>x=1/4:47/380=95/47

\(a,-\dfrac{4}{5}=-0,8\) \(;\dfrac{2}{10}=0,2\) \(\Rightarrow\) Ko bằng nhau

\(b,\dfrac{3}{2}=1,5;\dfrac{9}{6}=\dfrac{3}{2}=1,5\Rightarrow\) Bằng nhau

\(c,\dfrac{1}{-2}=-0,5;-\dfrac{40}{80}=-\dfrac{1}{2}=-0,5\Rightarrow\) Bằng nhau

\(d,-\dfrac{12}{5}=-2,4;-\dfrac{144}{25}=-5,76\Rightarrow\) Ko bằng nhau

\(e,\dfrac{2525}{4343}=\dfrac{25}{43};\dfrac{25}{43}=\dfrac{25}{43}\)\(\Rightarrow\) Bằng nhau

\(f,-\dfrac{26}{17}\approx-1,53;\dfrac{262626}{171717}=\dfrac{26}{17}\approx1,53\) \(\Rightarrow\) Ko bằng nhau

\(=\dfrac{13}{17}\cdot\dfrac{17}{19}\cdot\dfrac{19}{13}=1\)

=1

1

a,2/3 * 3/4 * 4/5 * 5/6

  Giản ước 3 với 3 , 4 với 4 , 5 với 5

=>2/3 * 3/4 * 4/5 * 5/6=2/6=1/3

b,5454/5757-171717/191919

=54/57-17/19

Quy đồng:54/57-(17*3/19*3)

               =54/57-51/57

               =3/57=1/19

NHỚ CLICK ĐÚNG CHO MÌNH NHA!!!!

a,2/3 * 3/4 * 4/5 * 5/6

  Giản ước 3 với 3 , 4 với 4 , 5 với 5

=>2/3 * 3/4 * 4/5 * 5/6=2/6=1/3

b,5454/5757-171717/191919

=54/57-17/19

Quy đồng:54/57-(17*3/19*3)

               =54/57-51/57

               =3/57=1/19

a,2/3 * 3/4 * 4/5 * 5/6

  Giản ước 3 với 3 , 4 với 4 , 5 với 5

=>2/3 * 3/4 * 4/5 * 5/6=2/6=1/3

b,5454/5757-171717/191919

=54/57-17/19

Quy đồng:54/57-(17*3/19*3)

               =54/57-51/57

               =3/57=1/19

1) a) \(\frac{5454}{5757}-\frac{171717}{191919}=\frac{18\times3\times101}{19\times3\times101}-\frac{17\times10101}{19\times10101}=\frac{18}{19}-\frac{17}{19}=\frac{1}{19}\)

b) \(\frac{6}{5}\times\frac{7}{6}\times\frac{8}{7}\times....\times\frac{2021}{2020}=\frac{6\times7\times8\times...\times2021}{5\times6\times7\times...\times2020}=\frac{2021}{5}\)

2) \(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{1}{45}=2\times\frac{1}{6}+2\times\frac{1}{12}+2\times\frac{1}{20}+...+2\times\frac{1}{90}\)

\(=2\times\left(\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{90}\right)\)

\(=2\times\left(\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+...+\frac{1}{9\times10}\right)\)

\(=2\times\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{9}-\frac{1}{10}\right)=2\times\left(\frac{1}{2}-\frac{1}{10}\right)=2\times\frac{2}{5}=\frac{4}{5}\)

b)Vì \(a-1< a+1\)

=> \(\frac{1}{a-1}>\frac{1}{a+1}\)

1/ a x b = 1/a - 1/b 

đk : b - a = 1

Môn Toán nha mọi người, mình nhầm!

\(\dfrac{5454}{5757}-\dfrac{171717}{191919}=\dfrac{1}{19}\)

\(\dfrac{2}{19}\)

GIUP MINH VOI

a) \(3\left(x-4\right)-\left(8-x\right)=12\)

\(3x-12-8+x=12\)

\(4x=12+12+8\)

\(4x=32\)

\(x=8\)

b) \(4\left(x-5\right)-\left(x-7\right)=-19\)

\(4x-20-x+7=-19\)

\(3x=-19+20-7\)

\(3x=-6\)

\(x=-2\)

c) \(7\left(x-3\right)-5\left(3-x\right)=11x-5\)

\(7\left(x-3\right)+5\left(x-3\right)=11x-5\)

\(\left(x-3\right).12=11x-5\)

\(12x-36-11x+5=0\)

\(x-31=0\)

\(x=31\)

a) \(\frac{25}{53}:\frac{2525}{5353}:\frac{252525}{535353}\)

rút gọn 2 phân số phía sau

 \(\frac{2525}{5353}\)  chia cả tử và mẫu cho \(101\)

\(\frac{252525}{535353}\)chia cả tử và mẫu cho \(10101\)

b) tương tự câu a) nhé

1717/1919 = 17.101/19.101

171717/191919 = 17.10101/19.10101

→ 17/19 = 1717/1919 = 171717/191919

Ta thay : 17/19 = 17x1/19x1

              1717/1919 = 17x101/19x101

              171717/191919 = 17x10101/19x10101

Nen 17/19 = 1717/1919 = 171717/191919.

 Nho k minh nha!

Ta thay : 17/19 = 17x1/19x1

              1717/1919 = 17x101/19x101

              171717/191919 = 17x10101/19x10101

Nen 17/19 = 1717/1919 = 171717/191919.

 Nho k minh nha!