So sánh:
A = 2014x 2015 /2015+ 2014 + 1998 x 1998/ 1998 + 1999 và B = 2014x 2015 /2015+ 2014 + 1999 x 1999/ 1998 + 1999
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
1) (1998.1999 - 1998.1998 - 1900 - 98) : 2016
= [1998.(1999 - 1) - 1998) : 2016
= (1998 - 1998) : 2016
= 0 : 2016
= 0
2) 2015.2015 - 2013.2017
= 20152 - (2015 - 2).(2015 + 2)
= 20152 - (20152 - 22)
= 20152 - 20152 + 4
= 4
\(A=\dfrac{1999^{1999}+1}{1999^{1998}+1}\)
\(\dfrac{1}{1999}A=\dfrac{1999^{1999}+1}{1999^{1999}+1999}\)
\(\dfrac{1}{1999}A=\dfrac{1999^{1999}}{1999^{1999}}-\dfrac{1998}{1999^{1999}+1999}\)
\(\dfrac{1}{1999}A=1-\dfrac{1998}{1999^{1999}+1999}\)
\(B=\dfrac{1999^{2000}+1}{1999^{1999}+1}\)
\(\dfrac{1}{1999}B=\dfrac{1999^{2000}+1}{1999^{2000}+1999}\)
\(\dfrac{1}{1999}B=\dfrac{1999^{2000}}{1999^{2000}}-\dfrac{1998}{1999^{2000}+1999}\)
\(\dfrac{1}{1999}B=1-\dfrac{1998}{1999^{2000}+1999}\)
Vì \(\dfrac{1998}{1999^{1999}+1999}>\dfrac{1998}{1999^{2000}+1999}=>\dfrac{1}{1999}A< \dfrac{1}{1999}B=>A< B\)
\(A=\dfrac{1999^{1999}+1}{1999^{1998}+1}=\dfrac{\left(1999^{1999}+1\right)^2}{\left(1999^{1998}+1\right)\left(1999^{1999}+1\right)}\)
\(A=\dfrac{\left(1999^{1999}\right)^2+2.1999^{1999}+1}{\left(1999^{1998}+1\right)\left(1999^{1999}+1\right)}\left(1\right)\)
\(B=\dfrac{1999^{2000}+1}{1999^{1999}+1}=\dfrac{\left(1999^{2000}+1\right)\left(1999^{1998}+1\right)}{\left(1999^{1998}+1\right)\left(1999^{1999}+1\right)}\)
\(B=\dfrac{\left(1999.1999^{1999}+1\right)\left(\dfrac{1}{1999}.1999^{1999}+1\right)}{\left(1999^{1998}+1\right)\left(1999^{1999}+1\right)}\)
\(B=\dfrac{\left(1999^{1999}\right)^2+1999.1999^{1999}+\dfrac{1}{1999}.1999^{1999}+1}{\left(1999^{1998}+1\right)\left(1999^{1999}+1\right)}\)
\(B=\dfrac{\left(1999^{1999}\right)^2+\left(1999+\dfrac{1}{1999}\right).1999^{1999}+1}{\left(1999^{1998}+1\right)\left(1999^{1999}+1\right)}\left(2\right)\)
mà \(\left(1999+\dfrac{1}{1999}\right)>2\)
\(\left(1\right).\left(2\right)\Rightarrow A< B\)
(1/1997)x(1/1998)x(1/1999)x..........x(1/2015)
giải giúp mình nhé mình cần vào tối nay hoặc chiều nay
a)1999*2000-1:1998+1999*2000=[(1999*2000)-(1999*2000)] va 1:1998
=0 + 1998
=1998