.

Giúp trở lời đầy đủ

\(6\times\dfrac{3}{5}=\dfrac{18}{5};\dfrac{7}{2}+\dfrac{3}{10}=\dfrac{35}{10}+\dfrac{3}{10}=\dfrac{38}{10}=\dfrac{19}{5}\\ Ta.có:\dfrac{1}{10}< \dfrac{1}{2}< \dfrac{3}{5}< \dfrac{7}{10}< \dfrac{9}{10}< \dfrac{9}{7}< \dfrac{9}{5}< 3< \dfrac{18}{5}< \dfrac{19}{5}\\ \Leftrightarrow\dfrac{1}{10}< \dfrac{1}{2}< \dfrac{3}{5}< \dfrac{7}{10}< \dfrac{9}{10}< \dfrac{9}{7}< \dfrac{9}{5}< 3< 6\times\dfrac{3}{5}< \dfrac{7}{2}+\dfrac{3}{10}\)

\(\overline{ab}x15=\overline{7ab}< =>\overline{ab}x15=700+\overline{ab}< =>14x\overline{ab}=700\)

=>\(\overline{ab}=700:14=50\)

50 x 15 = 750

ab = 50

 x+(x+1)+(x+2)+....+(x+100)=20869

=> 101x + ( 100-1) nhân 100 : 2 = 20869

=> 101x +4950 = 20869

=> 101x = 20869-4950

=> 101x =15 919

=> x =15 919:101 =15919/101

Vậy x = 15919/101

Số xấu quá bạn

x+(x+1)+(x+2)+...+(x+100)=20869

x+(x x 100)+(1+2+3+...+100)=20869

(x x 101)+(100x(100+1)=20869

(x x 101)+(100x101)=20869

(x x 101)+10100=20869

x x 101=20869-10100

x x 101=10769

x=10769:101

x=\(\dfrac{10769}{101}\)

2 phần nha

2 phần nha

haizz☹

vô đây hỏi nè

(1/1-1/3+1/3-1/5+...+1/19-1/20)*63-x=20

(1/1-1/20)*63-x=20

19/20*63-x=20

1177/20-x=20

58,85-x=20

x=58,85-20

x=38,85

kich dung nha

              Đặt \(A=\frac{1}{1.3}+\frac{1}{3.5}+...+\frac{1}{19.21}\)

              \(2A=\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{19.21}\)

             \(2A=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{19}-\frac{1}{21}\)

              \(2A=1-\frac{1}{21}\)

              \(A=\frac{20}{21}:2\)

            \(A=\frac{10}{21}\)

          => \(\frac{10}{21}\)x 63 - x = 20

         => 30 - x = 20

        => x = 30 - 20 = 10

      Vậy x = 10

     Ủng hộ mk nha !!! ^_^

= 7800 nha 

78x45+78x65-78x9-78

= 78x(45+65-9-1)

=78x100

=7800