Ta có: \(\frac{\overline{ab}}{a+b}=\frac{\overline{bc}}{b+c}\)

\(\Leftrightarrow\frac{10a+b}{a+b}=\frac{10b+c}{b+c}\)

\(\Leftrightarrow\left(10a+b\right)\cdot\left(b+c\right)=\left(a+b\right)\cdot\left(10b+c\right)\)

\(\Leftrightarrow10ab+10ac+b^2+bc=10bc+ac+10b^2+bc\)

\(\Leftrightarrow9ac=9b^2\Rightarrow ac=b^2\)

\(\Rightarrow\frac{a}{b}=\frac{b}{c}\left(ĐPCM\right)\)

2,46 : 4 + 2,46 x 0,75

= 2,46 x 0,25 + 2,46 x 0,75

= 2,46 x ( 0,25 + 0,75 )

= 2,46 x 1

= 2,46

\(2,46:4+2,46\times0,75\)

\(=2,46:\frac{4}{1}+2,46\times0,75\)

\(=2,46\times\frac{1}{4}+2,46\times0,75\)

\(=2,46\times\left[\frac{1}{4}+0,75\right]\)

\(=2,46\times\left[0,25+0,75\right]=2,46\)

\(\frac{50}{51}\cdot\frac{51}{15}:\frac{34}{15}\)

\(=\frac{50}{51}\cdot\frac{51}{15}\cdot\frac{15}{34}=\frac{50\cdot51\cdot15}{51\cdot15\cdot34}=\frac{50}{34}=\frac{25}{17}\)

\(\frac{50}{51}.\frac{51}{15}:\frac{34}{15}\)

\(=\frac{50.51.15}{51.15.34}\)

\(=\frac{50}{34}=\frac{25}{17}\)

\(\left(\frac{3}{8}+\frac{-3}{4}+\frac{7}{12}\right):\frac{5}{6}+\frac{1}{2}\)

\(=\frac{5}{24}.\frac{6}{5}+\frac{1}{2}\)

\(=\frac{1}{4}+\frac{1}{2}\)

\(=\frac{3}{4}\)

\(\left[\frac{3}{8}+\frac{-3}{4}+\frac{7}{12}\right]:\frac{5}{6}+\frac{1}{2}\)

\(=\left[\frac{3\cdot3}{24}+\frac{-3\cdot6}{24}+\frac{7\cdot2}{24}\right]:\frac{5}{6}+\frac{1}{2}\)

\(=\left[\frac{9}{24}+\frac{-18}{24}+\frac{14}{24}\right]:\frac{5}{6}+\frac{1}{2}\)

\(=\left[\frac{9+(-18)+14}{24}\right]:\frac{5}{6}+\frac{1}{2}\)

\(=\frac{5}{24}:\frac{5}{6}+\frac{1}{2}\)

\(=\frac{5}{24}\cdot\frac{6}{5}+\frac{1}{2}=\frac{1}{4}+\frac{1}{2}=\frac{1}{4}+\frac{1\cdot2}{4}=\frac{1}{4}+\frac{2}{4}=\frac{3}{4}\)

 bằng 20

Theo đề bài,đặt \(x+y=k\inℤ\) (1)

\(\frac{1}{x}+\frac{1}{y}=\left(x+y\right).\frac{1}{xy}=k.\frac{1}{xy}\)

Do k nguyên (theo (1)) nên để \(\frac{1}{x}+\frac{1}{y}\) nguyên thì \(\frac{1}{xy}\) nguyên

Nên \(xy\inƯ\left(1\right)=\left\{1;-1\right\}\)

Suy ra \(\left(x;y\right)=\left(1;1\right),\left(-1;-1\right),\left(1;-1\right),\left(-1;1\right)\)

Đúng không ta?

ơ,t sai rồi=( nếu làm như t sẽ bị thiếu nghiệm,chẵn hạn x =y = 2 hoặc x = 2 ; y = -2=.Ai có cách khác giúp với ạ!

tao biet nhung tao khong noi dau

nói đi m