1a) x - 1/3 = 13/6

          x  = 13/6 + 1/3

          x  = 5/2

b) -7/5 - x = 13/7 : 13/7

    -7/5 - x = 1

             x = -7/5 - 1

             x = -12/5

2) A = 1/1.2 + 1/2.3 + 1/3.4 + ... + 1/2015.2016

A = 1 -1/2 + 1/2 - 1/3 + 1/3 - 1/4 + ... + 1/2015 - 1/2016

A = 1 - 1/2016

A = 1 - 1/2016

A = 2015/2016

các bạn giúp mình nhé

bằng 2/15 mình làm trên violimpic rồi

a) \(\frac{1}{3}-\frac{3}{4}-\left(\frac{-3}{5}\right)+\frac{1}{64}-\frac{2}{9}-\frac{1}{36}+\frac{1}{15}\)

=\(\left(\frac{1}{3}+\frac{3}{5}+\frac{1}{15}\right)-\left(\frac{3}{4}+\frac{2}{9}+\frac{1}{36}\right)+\frac{1}{64} \)

=\(\frac{5+9+1}{15}-\frac{27+8+1}{36}+\frac{1}{64}\)

= \(1+1+\frac{1}{64}=2\frac{1}{64}\)

Ta có : 

\(A=\frac{3^9-2^3.3^7+2^{10}.3^2-2^{13}}{3^{10}-2^2.3^7+2^{10}.3^3-2^{12}}\)

\(A=\frac{3^7\left(3^2-2^3\right)+2^{10}\left(3^2-2^3\right)}{3^7\left(3^3-2^2\right)+2^{10}\left(3^3-2^2\right)}\)

\(A=\frac{\left(3^2-2^3\right)\left(3^7+2^{10}\right)}{\left(3^3-2^2\right)\left(3^7+2^{10}\right)}\)

\(A=\frac{3^2-2^3}{3^3-2^2}\)

\(A=\frac{9-8}{27-4}\)

\(A=\frac{1}{23}\)

Vậy \(A=\frac{1}{23}\)

Chúc bạn học tốt ~ 

\(\frac{5}{6}+\frac{7}{13}+\frac{17}{9}+\frac{19}{13}+\frac{1}{9}+\frac{7}{6}\)

\(=\left(\frac{5}{6}+\frac{7}{6}\right)+\left(\frac{17}{9}+\frac{1}{9}\right)+\left(\frac{19}{13}+\frac{7}{13}\right)\)

\(=\frac{12}{6}+\frac{18}{9}+\frac{26}{13}\)

\(=2+2+2\)

\(=4+2\)

\(=6\)

\(\frac{5}{6}+\frac{7}{13}+\frac{17}{9}+\frac{19}{13}+\frac{1}{9}+\frac{7}{6}.\)

\(=\left(\frac{5}{6}+\frac{7}{6}\right)+\left(\frac{7}{13}+\frac{19}{13}\right)+\left(\frac{17}{9}+\frac{1}{9}\right)\)

\(=\frac{12}{6}+\frac{26}{13}+\frac{18}{9}\)

\(=2+2+2\)

\(=6\)

a, 13/6+5/8 : -3/4 - 7/12.4

= 13/6 + -5/6-7/3

=8/6-7/3

= -6/6

= -1

b, ( 73/5 - 21/3) + ( 4/3-43/5 )

= 73/5-21/3+4/3-43/5

=( 73/5-43/5)-(21/3-4/3)

= 6-17/3

=1/3

c, 7/5.4/9 +7/5: 9/16- 14/10.2/9

= 7/5.4/9 +7/5.16/9 - 14/45

=7/5.(4/9+16/9)-14/45

=7/5.20/9-14/45

= 140/45 - 14/45

= 126/45

Xong rùi nè! Nhưng bạn kiểm tra lại giùm nhé vì làm vào ban đêm nên hơi bất tiện

Trời ạ. 7 3/5 chứ k phải 73/5 -_-

xin lỗi đây là bài tính hợp lí nhé