so sánh: a) A= 13^15+1 / 13^16+1 B= 13^16+1 / 13^17+1 b) C= 10 ^ 2020+5 / 10^2020-8 D= 10 ^2021+5 / 10^2021-8

0 bình luận về “so sánh: a) A= 13^15+1 / 13^16+1 B= 13^16+1 / 13^17+1 b) C= 10 ^ 2020+5 / 10^2020-8 D= 10 ^2021+5 / 10^2021-8”

1. `a. A=(13^{15}+1)/(13^{16}+1)`

   `⇒13A=(13^{16}+13)/(13^{16}+1)`

   `⇒13A=1+(12)/(13^{16}+1)`

   `B=(13^{16}+1)/(13^{17}+1)`

   `⇒13B=(13^{17}+13)/(13^{17}+1)`

   `⇒13B=1+(12)/(13^{17}+1)`

   Ta có: `(12)/(13^{16}+1)>(12)/(13^{17}+1)`

   `⇒1+(12)/(13^{16}+1)>1+(12)/(13^{17}+1)`

   $⇒13A>13B$

   $⇒A>B$

   Vậy $A>B$

   `b. C=(10^{2020}+5)/(10^{2020}-8)`

   `⇒C=((10^{2020}-8)+13)/(10^{2020}-8)`

   `⇒C=1+(13)/(10^{2020}-8)`

   `D=(10^{2021}+5)/(10^{2021}-8)`

   `⇒D=((10^{2021}-8)+13)/(10^{2021}-8)`

   `⇒D=1+(13)/(10^{2021}-8)`

   Ta có: `(13)/(10^{2020}-8)>(13)/(10^{2021}-8)`

   `⇒1+(13)/(10^{2020}-8)>1+(13)/(10^{2021}-8)`

   $⇒C>D$

   Vậy $C>D$.

   Trả lời

2. a)Ta có 13A=(13^16+13)/(13^16+1)=1+  12/(13^16+1)

   Ta có 13B=(13^17+13) / (13^17+1)=1+  12/(13^17+1)

   Vì 1+  12/(13^16+1)>1+  12/(13^17+1)

   Vậy A>B

   b)C= 10 ^ 2020+5 / 10^2020-8>D=  10 ^2021+5 / 10^2021-8

   nhìn là bít mà bn!!!

    

   Trả lời