(26/19 - 7/19)x ( 8/11+3/11)

= 1x1 

=1

\(\Leftrightarrow3.\left(\frac{16}{36}\right)^x+2.\left(\frac{81}{36}\right)^x=5\)

\(\Leftrightarrow3\left(\frac{4}{9}\right)^x+2.\left(\frac{9}{4}\right)^x-5=0\)

Đặt \(\left(\frac{4}{9}\right)^x=a>0\) phương trình trở thành:

\(3a+\frac{2}{a}-5=0\Leftrightarrow3a^2-5a+2=0\Rightarrow\left[{}\begin{matrix}a=1\\a=\frac{2}{3}\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}\left(\frac{4}{9}\right)^x=1\\\left(\frac{4}{9}\right)^x=\frac{2}{3}\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=0\\x=\frac{1}{2}\end{matrix}\right.\)

(1-3)+(5-7)+(9-11)+....+(17-19)

=(-2)+(-2)+(-2)+...+(-2)

=(-2)x5

=-10

\(A=\frac{6}{19}.\left(\frac{-7}{11}\right)+\frac{6}{19}.\left(\frac{-4}{11}\right)-\frac{13}{19}\)

\(A=\frac{6}{19}.\left(\frac{-7}{11}-\frac{4}{11}\right)-\frac{13}{19}\)

\(A=\frac{-6}{19}-\frac{13}{19}\)

\(A=\frac{-19}{19}\)

\(A=-1\)

vậy \(A=-1\)

\(=\dfrac{3}{7}\cdot\dfrac{7}{3}\cdot\dfrac{-2}{5}\cdot20\cdot\dfrac{19}{72}=-8\cdot\dfrac{19}{72}=-\dfrac{19}{9}\)

a) \(\dfrac{\dfrac{3}{14}-\dfrac{3}{17}+\dfrac{3}{19}}{\dfrac{5}{19}+\dfrac{5}{14}-\dfrac{5}{17}}=\dfrac{3\left(\dfrac{1}{14}-\dfrac{1}{17}+\dfrac{1}{19}\right)}{5\left(\dfrac{1}{14}-\dfrac{1}{17}+\dfrac{1}{19}\right)}=\dfrac{3}{5}\)

c) \(\dfrac{\dfrac{2}{7}+\dfrac{2}{5}+\dfrac{2}{17}-\dfrac{2}{193}}{\dfrac{3}{7}+\dfrac{3}{5}+\dfrac{3}{17}-\dfrac{3}{293}}=\dfrac{2\left(\dfrac{1}{7}+\dfrac{1}{5}+\dfrac{1}{17}-\dfrac{1}{193}\right)}{3\left(\dfrac{1}{7}+\dfrac{1}{5}+\dfrac{1}{17}-\dfrac{1}{193}\right)}=\dfrac{2}{3}\)

d) 

ai tk mình đi mk bị âm

\(\dfrac{4}{5}\)+\(\dfrac{-5}{4}\)=\(\dfrac{0}{4}\)

\(\dfrac{-1}{3}\)+\(\dfrac{2}{5}-\dfrac{5}{6}\)=\(\dfrac{-10}{30}+\dfrac{12}{30}-\dfrac{25}{30}\)=\(\dfrac{-23}{30}\)

\(\dfrac{2}{3}-\dfrac{5}{7}.\dfrac{14}{25}\)=\(\dfrac{2}{3}-\dfrac{2}{5}\)=\(\dfrac{10}{15}-\dfrac{6}{15}\)=\(\dfrac{4}{15}\)

Gigachad cảm ơn bạn sai rồi

1. TÍNH 

`5/7 xx 4 : 5/9 = 5/7 xx 4 xx 9/5 = 20/7 xx 9/5 = 36/7`

`4/9 : 2 xx 5/7 = 4/9 xx 1/2 xx 5/7 = 2/9 xx 10/63 `

`8 xx 2/3 : 1/2= 8xx 2/3 xx 2/1 = 8 xx 2/3 xx 2 = 16/3 xx 2=32/3`