\(a,\\ Ta.có:\dfrac{16}{-19}< 0;\dfrac{15}{17}>0\\ \Rightarrow\dfrac{16}{-19}< \dfrac{15}{17}\\ b,\\ Ta.có:\dfrac{419}{-723}< 0;\dfrac{-697}{-313}>0\\ \Rightarrow\dfrac{419}{-723}< \dfrac{-697}{-313}\\ c,\dfrac{311}{256}>\dfrac{256}{256}=1;\dfrac{199}{293}< \dfrac{203}{203}=1\\ \Rightarrow\dfrac{311}{256}>\dfrac{199}{203}\)

Ta có : 

\(\frac{19}{60}< \frac{20}{60}=\frac{1}{3}\)

\(\frac{31}{90}>\frac{30}{90}=\frac{1}{3}\)

=> \(\frac{31}{90}>\frac{1}{3}>\frac{19}{60}\Rightarrow\frac{31}{90}>\frac{19}{60}\)

a ) 16 − 19 < 0 < 15 17 b ) 419 − 723 < 0 < − 697 − 313

c ) 311 256 > 1 > 199 203 d ) 30 235 = 6 47 > 6 48 = 8 64 > 8 63 = 168 1323 e ) 19 60 < 20 60 = 30 90 < 31 90 f ) 15 23 > 14 23 = 70 115 > 70 117

15/12 < 16/15

dấu < nha

HT

15/12<16/15 nha

HT

cách 1 : Phần bù

cách 2 : qui đồng

Vì 4/5<1,5/3>1=>4/5<5/3

Vì 15/22<19/22,19/21>19/22=>15/22<19/21

C1 : Tử số chung nhỏ nhất là 72

Ta có : \(\frac{8}{15}=\frac{8.9}{15.9}=\frac{72}{135}\); \(\frac{9}{16}=\frac{9.8}{16.8}=\frac{72}{128}\)

Vì \(\frac{72}{135}

\(\frac{8}{15}và\frac{9}{16}\)

C1 : \(1-\frac{8}{15}=\frac{7}{15}\)

\(1-\frac{9}{16}=\frac{7}{16}\)

Vì \(\frac{7}{15}>\frac{7}{16}nên\frac{8}{15}

a)  311 256 > 1 > 199 203

b)  30 235 = 6 47 > 6 48 = 8 64 > 8 63 = 168 1323