\(\frac{7-x}{2}+\frac{2}{3}.\left(x-7\right)\left(x-3\right)=0\)

\(\Leftrightarrow\frac{x-7}{-2}+\frac{2\left(x-7\right)}{3}\left(x-3\right)=0\)

\(\Leftrightarrow\left(x-7\right)\left[\frac{-1}{2}+\frac{2}{3}\left(x-3\right)\right]=0\)

\(\Leftrightarrow\left(x-7\right)\left(\frac{-1}{2}+\frac{2x}{3}-2\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x-7=0\\\frac{-1}{2}+\frac{2x}{3}-2=0\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=7\\-\frac{5}{2}+\frac{2x}{3}=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=7\\\frac{2x}{3}=\frac{5}{2}\end{cases}\Leftrightarrow\orbr{\begin{cases}x=7\\x=\frac{15}{4}\end{cases}}}\)

Bài 1: 

a: \(\dfrac{25}{42}-\dfrac{20}{63}=\dfrac{75-40}{126}=\dfrac{35}{126}=\dfrac{5}{18}\)

b: \(\dfrac{9}{20}-\dfrac{13}{75}-\dfrac{1}{6}=\dfrac{135}{300}-\dfrac{52}{300}-\dfrac{50}{300}=\dfrac{33}{300}=\dfrac{11}{100}\)

Ca này bó tay rồi, ghi rõ ra đc ko, khó hiểu quá

6 2/7  + 7 3/5 + 8 6/9 + 9 1/4 + 2/5 +  5/7 + 1/3  x 3/4 + 1967

= 44/7 + 38/5 + 78/9 + 37/4 + 2/5 + 5/7 + 1/3 + 1967

= ( 44/7 + 5/7 ) + ( 38/5 + 2/5 ) + ( 26/3 + 1/3 ) + ( 37/4 + 3/4 )  +1967

=  7 + 8 + 9 + 10  + 1967

= 15  + 9 + 10 + 1967

= 24 + 10 + 1967

= 34 + 1967 

= 2001

tính nhanh lớp 6 20 nhân 17-4 nhân 5 nhân 7

\(\left(x+\frac{2}{7}\right)+\frac{1}{3}=-2\)

\(x+\frac{13}{21}=-2\)

\(x=-2-\frac{13}{21}\)

\(x=\frac{-55}{21}\)

292/175

\(\frac{2}{5}\times\frac{3}{5}+\frac{4}{7}:\frac{1}{3}-\frac{2}{7}\)

\(=\frac{6}{25}+\frac{12}{7}-\frac{2}{7}\)

\(=\frac{6}{25}+\frac{10}{7}\)

\(=\frac{292}{175}\)

k tớ nha

sẽ bằng số \(\frac{256}{125}\)

k nha cảm ơn