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
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
By Savannah
By Savannah
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
`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 $C>D$.
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!!!