a) Ta có : 
\(\underbrace{99...9}5 = 5 \times 1 \underbrace{99...9}\)
100 chữ số 9            100 chữ số 9
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b: \(\dfrac{121212}{424242}=\dfrac{12}{42}=\dfrac{2}{7}\)

c: \(\dfrac{187187187}{221221221}=\dfrac{187}{221}=\dfrac{11}{13}\)

Đặt \(A=\frac{3\cdot7\cdot13\cdot37\cdot39-10101}{505050-70707}\)

\(A=\frac{\left(3\cdot7\cdot13\cdot37\right)\cdot39-10101\cdot1}{50\cdot10101+7\cdot10101}\)

\(A=\frac{10101\cdot39-10101\cdot1}{10101\cdot\left(50+7\right)}\)

\(A=\frac{10101\cdot\left(39-1\right)}{10101\cdot57}\)

\(A=\frac{10101\cdot38}{10101\cdot57}\)

\(A=\frac{38}{57}=\frac{38:19}{57:19}=\frac{2}{3}\)

_{10101(39-1)/10101(50+7)=2/3 bn}

\(\frac{2}{3}\)

\(\frac{3.7.13.37.19-10101}{505050+70707}\)=\(\frac{10101.39-10101}{10101.50+10101.7}\)=\(\frac{10101.\left(39-1\right)}{10101.\left(50+7\right)}\)=\(\frac{38}{57}\)=\(\frac{2}{3}\)

\(\frac{3.7.13.37.39-10101}{505050+70707}\)

\(=\frac{\left(3.7.13.37\right).39-10101}{50.10101+7.10101}\)

\(=\frac{10101.39-10101.1}{\left(50+7\right).10101}\)

\(=\frac{\left(39-1\right).10101}{57.10101}\)

\(=\frac{38.10101}{57.10101}\)

\(=\frac{38}{57}=\frac{38:19}{57:19}=\frac{2}{3}\)

A=10101*39-10101/505050+70707

A=10101(39-1)/10101(50+7)

A=38/57=2/3(chia cả tử và mẫu cho 10101)

cho tui đáp số đây đáp số kia lộn

\(\frac{45}{6}\)

45/6

Ta có:

\(\frac{3.7.13.37.39-10101}{505050-70707}=\frac{10101.39-10101}{505050-70707}=\frac{10101\left(39-1\right)}{10101\left(50-7\right)}=\frac{39-1}{50-7}=\frac{38}{43}\)

38/43 đó

rút gọn cái gì

so to the ai ma rut gon đc

các bn chuẩn bị gậy để chống sau khi rút gọn dc con số này nhé