So sánh các ps sau bằng cách dùng phân số chung gian:
a) 23/21 ; 21/23
b) -15/-17 ; 16/19
c) 59/101 ; 56/105
d) 14/55 ; 19/84
So sánh các ps sau bằng cách dùng phân số chung gian:
a) 23/21 ; 21/23
b) -15/-17 ; 16/19
c) 59/101 ; 56/105
d) 14/55 ; 19/84
Đáp án:
a)
$\dfrac{23}{21}>\dfrac{23}{23}>\dfrac{21}{23}$
$\Rightarrow \dfrac{23}{21}>\dfrac{21}{23}$
b)
$\dfrac{-15}{-17}=\dfrac{15}{17}>0$
$\dfrac{16}{-19}<0$
$\Rightarrow \dfrac{-15}{-17}>\dfrac{16}{-19}$
c)
$\dfrac{59}{101}>\dfrac{59}{105}>\dfrac{56}{105}$
$\Rightarrow \dfrac{59}{101}>\dfrac{56}{105}$
d)
$\dfrac{14}{55}>\dfrac{14}{56}=\dfrac{21}{84}>\dfrac{19}{84}$
$\Rightarrow \dfrac{14}{55}>\dfrac{19}{84}$