4/9<1/2

4/9<1/2

a) ta có:  \(1-\frac{2012}{2013}=\frac{1}{2013}\)

                 \(1-\frac{2013}{2014}=\frac{1}{2014}\)

mà \(\frac{1}{2013}>\frac{1}{2014}\) nên   \(\frac{2013}{2014}>\frac{2012}{2013}\)

sao giống lớp 4 thế ta

\(\dfrac{1313}{1717}=\dfrac{101x13}{101x17}=\dfrac{13}{17}\)

\(\dfrac{131313}{171717}=\dfrac{10101x13}{10101x17}=\dfrac{13}{17}\)

Vậy \(\dfrac{1313}{1717}=\dfrac{131317}{171717}\)

\(\dfrac{1313}{1717}và\dfrac{131313}{171717}\\ \dfrac{1313}{1717}=\dfrac{13}{17}\\ \dfrac{131313}{171717}=\dfrac{13}{17}\\ \Rightarrow\dfrac{1313}{1717}=\dfrac{131313}{171717}\)

1313/1717=131313/171717

+ \(\frac{2000}{2001}=\frac{2001-1}{2001}=1-\frac{1}{2001}\)

+ \(\frac{2001}{2002}=\frac{2002-1}{2002}=1-\frac{1}{2002}\)

+ \(\frac{1}{2001}>\frac{1}{2002}\Rightarrow1-\frac{1}{2001}

\(1-\frac{2000}{2001}=\frac{1}{2001}\)

\(1-\frac{2001}{2002}=\frac{1}{2002}\)

Vì \(\frac{1}{2001}>\frac{1}{2002}\) nên  \(\frac{2000}{2001}

Quá dễ

Ta có: 201/301>201/308; 201/308>199/308

\(\Rightarrow\)201/301>199/308

Ta có : 

\(\frac{201}{301}>\frac{201}{308}\left(301< 308\right)\)

Mà \(\frac{199}{308}< \frac{201}{308}\left(199< 201\right)\)

\(\Rightarrow\frac{201}{301}>\frac{199}{308}\)

Chúc bạn học tốt !!!! 

\(\frac{201}{301}>\frac{199}{301}>\frac{199}{308}\)   Vậy,   \(\frac{201}{301}>\frac{199}{308}\)

Không quy đồng tử số và mẫu số , hãy so sánh các phân số sau : 2012/ 2013 và 1998 / 1999

 2012/ 2013 > 1998 / 1999

DỄ MÀ

2012/2013>1998/1999 HOẶC 2012/2013 < 1998/1999

\(\frac{2012}{2013}\)và \(\frac{1998}{1999}\).

Lại có:

\(\frac{2012}{2013}=\frac{2013-1}{2013}=1-\frac{1}{2013}\).

\(\frac{1998}{1999}=\frac{1999-1}{1999}=1-\frac{1}{1999}\).

Mà \(\frac{1}{2013}< \frac{1}{1999}\)\(\Rightarrow\frac{-1}{2013}>\frac{-1}{1999}\).

\(\Rightarrow1-\frac{1}{2013}>1-\frac{1}{1999}\).

Do đó\(\frac{2012}{2013}>\frac{1998}{1999}\).

Vậy \(\frac{2012}{2013}>\frac{1998}{1999}\)

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