so sanh A=9^10;B=8^9+7^9+.......+2^9+1^9
A =9^9+1/9^10+1
B=10^9+1/10^10+1
so sanh a va b
A = 387420490 ; B = 1000000001
vậy B lớn hơn A
ko quy dong mau so hay so sanh: A=-9/10^2015+-19/10^2016 va -9/10^2016+-19/10^2015
so sanh A= -9/ 10^2016 + -19/ 10^2017; B = -9/10^2017+-19/10^2016
Cac ban giup may.khong quy dong so sanh;A=-9/10^2010+-9/10^2011 va B=-9/10^2011+-19/10^2010
\(A=\frac{-9}{10^{2011}}+\frac{-9}{10^{2010}}\)
\(B=\frac{-9}{10^{2011}}+\frac{-19}{10^{2010}}\)
\(\frac{-9}{10^{2010}}>\frac{-19}{10^{2010}}\)
\(\Rightarrow\frac{-9}{10^{2011}}+\frac{-9}{10^{2010}}>\frac{-9}{10^{2011}}+\frac{-19}{10^{2010}}\)
\(\Rightarrow A>B\)
so sanh : 2001/2004 va 39/40
so sanh : A = 1/6 + 1/7 + 1/8 + 1/9 + 1/10 voi B = 1
\(A< \frac{1}{5}+\frac{1}{5}+\frac{1}{5}+\frac{1}{5}+\frac{1}{5}=\frac{5}{5}=1=B\)
a/
\(\frac{2001}{2004}=\frac{2004-3}{2004}=1-\frac{3}{2004}=1-\frac{1}{668}.\)
\(\frac{39}{40}=\frac{40-1}{40}=1-\frac{1}{40}\)
Ta có \(40< 668\Rightarrow\frac{1}{40}>\frac{1}{668}\Rightarrow1-\frac{1}{40}< 1-\frac{1}{668}\Rightarrow\frac{39}{40}< \frac{2001}{2004}\)
b/
\(A< \frac{1}{5}+\frac{1}{5}+\frac{1}{5}+\frac{1}{5}+\frac{1}{5}=1=B\)
9/10........9+3/10+3
so sanh 2 phan so
9/10 ..... 9 + 3/10 + 3
9/10....... 12/13
9/10=117/130
12/13 = 120/130
Vì 120/130 > 117/130 Nên 9 + 3/10 + 3 > 9/10
cho A=10^7+1/10^8+1
B=10^8+1/10^9+1
so sanh A va B
các bạn giúp mình với nhanh lên nhé.Mình sẽ cho
Cho A=1/2!+2/3!+......+8/9!+9/10!.so sanh A voi1.Voi n!=1.2.3.....n(tich cua n so tu nhien khac 0 dau tien)
So sanh:1990^10+1990^9 và1991^10
(1990^10 + 1990^9) và 1991^10
1990^10 + 1990^9 = 1990.1990^9 + 1990^9 = 1991^9 < 1991^10
--> (1990^10 + 1990^9) < 1991^10