So sánh \(\dfrac{10^{2017}+1}{10^{2016}+1}\) và \(\dfrac{10^{2018}+1}{10^{2017}+1}\)
Cho \(A=\dfrac{10^{2016}+1}{10^{2017}+1}\) và \(B=\dfrac{10^{2017}+1}{10^{2018}+1}\)
So sánh A và B
10a=10^2017+10/10^2017+1
10b=10^2018+10/10^2018+1
cậu tự so sánh nhé vậy là dễ rồi
Ta có: \(A=\dfrac{10^{2016}+1}{10^{2017}+1}\Rightarrow10A=\dfrac{10\left(10^{2016}+1\right)}{10^{2017}+1}=\dfrac{10^{2017}+10}{10^{2017}+1}\)
\(=\dfrac{10^{2017}+1+9}{10^{2017}+1}=\dfrac{10^{2017}+1}{10^{2017}+1}+\dfrac{9}{10^{2017}+1}=1+\dfrac{9}{10^{2017}+1}\)
Tương tự ta cũng có: \(10B=1+\dfrac{9}{10^{2018}+1}\)
Lại có: \(10^{2017}< 10^{2018}\Rightarrow10^{2017}+1< 10^{2018}+1\)
\(\Rightarrow\dfrac{1}{10^{2017}+1}>\dfrac{1}{10^{2018}+1}\Rightarrow\dfrac{9}{10^{2017}+1}>\dfrac{9}{10^{2018}+1}\)
\(\Rightarrow1+\dfrac{9}{10^{2017}+1}>1+\dfrac{9}{10^{2018}+1}\Rightarrow10A>10B\Rightarrow A>B\)
so sánh A = 10 mũ 2017 + 1 / 10 mũ 2018 + 1 và B = 10 mũ 2016 +1 /10 mũ 2017
so sánh a và b biết a=2016/2017+2017/2018+2018/2019+2019/2016 và b=1/8+1/9+1/10+...+1/63
Cho A= 102016+1/102017+1;B=102017+1/102018+1
So sánh A và B
Ta có : \(10.A=\frac{10^{2017}+10}{10^{2017}+1}=\frac{10^{2017}+1+9}{10^{2017}+1}=\frac{10^{2017}+1}{10^{2017}+1}+\frac{9}{10^{2017}+1}=1+\frac{9}{10^{2017}+1}\)
\(10.B=\frac{10^{2018}+10}{10^{2018}+1}=\frac{10^{2018}+1+9}{10^{2018}+1}=\frac{10^{2018}+1}{10^{2018}+1}+\frac{9}{10^{2018}+1}=1+\frac{9}{10^{2018}+1}\)
Vì \(1=1\)và \(\frac{9}{10^{2017}+1}>\frac{9}{10^{2018}+1}\)nên \(1+\frac{9}{10^{2017}+1}>1+\frac{9}{10^{2018}+1}\)hay \(A>B\)
Vậy \(A>B\)
So sánh:
\(A=\frac{10^{2016}+1}{10^{2017}+1}\) và \(B=\frac{10^{2017}+1}{10^{2018}+1}\)
Ta có : \(A=\frac{10^{2016}+1}{10^{2017}+1}\)
Suy ra \(10A=\frac{10^{2017}+10}{10^{2017}+1}\)
Suy ra \(10A=1+\frac{9}{10^{2017}+1}\)
Ta lại có : \(B=\frac{10^{2017}+1}{10^{2018}+1}\)
Suy ra : \(10B=\frac{10^{2018}+10}{10^{2018}+1}\)
Suy ra : \(10B=1+\frac{9}{10^{2018}+1}\)
Vì \(\frac{9}{10^{2017}+1}>\frac{9}{10^{2018}+1}\)
Nên \(1+\frac{9}{10^{2017}+1}>1+\frac{9}{10^{2018}+1}\)
Suy ra \(10A>10B\)
Suy ra \(A>B\)
\(B< \frac{10^{2017}+1+9}{10^{2018}+1+9}=\frac{10^{2017}+10}{10^{2018}+10}=\frac{10\left(10^{2016}+1\right)}{10\left(10^{2017}+1\right)}=\frac{10^{2016}+1}{10^{2017}+1}=A\)
vậy A > B
so sánh A và B
A = 102016+1 /102017+1
B = 102017+1 / 102018+1
\(A=\frac{10^{2016}+1}{10^{2017}+1}\)
\(A=\frac{10^{2016}+1}{10^{2017}+1}+\frac{10^{2017}+1}{10^{2017}+1}\)
\(A=\frac{10^{2016}+1+10^{2017}+1}{10^{2017}+1}\)
\(A=\frac{10^{2016}+10^{2017}+1+1}{10^{2016}.10+1}\)
\(A=\frac{10^{2016}.\left(1+10\right)+2}{10^{2016}.10+1}\)
\(A=\frac{10^{2016}.11+2}{10^{2016}.10+1}\)
\(A=\frac{11+2}{10+1}\)
\(A=\frac{13}{11}\)(1)
Làm tương tự phần B
Từ 1 và 2
\(\Leftrightarrow\)\(\frac{13}{11}=\frac{13}{11}\)
\(\Leftrightarrow\)A = B
So sánh A và B, biết:
A =\(\frac{10^{2016}+1}{10^{2017}+1}\)và B =\(\frac{10^{2017}+1}{10^{2018}+1}\)
Nhân cả hai tử của \(A\)và \(B\)với 2 , ta được :
\(10A=10.\left(\frac{10^{2016}+1}{10^{2017}+1}\right)=\frac{10^{2017}+1+9}{10^{2017}+1}=1+\frac{9}{2^{2017}+1}\)
\(10B=10\left(\frac{10^{2017}+1}{10^{2018}+1}\right)=\frac{10^{2018}+10}{10^{2018}+1}=\frac{10^{2018}+1+9}{10^{2018}}=1+\frac{9}{10^{2018}+1}\)
Vì \(1=1;9=9\)
\(\Rightarrow\)Ta so sánh mẫu , ta có:
\(10^{2017}< 10^{2018}\)
\(\Rightarrow10^{2017}+1< 10^{2018}+1\)
\(\Rightarrow1+\frac{9}{10^{2017}+1}>1+\frac{9}{10^{2018}+1}\)
\(\Rightarrow10A>10B\)
Hay \(A>B\)
So sánh A=\(\frac{10^{2017}+1}{10^{ }^{2016}+1}\)B=\(\frac{10^{2018}+1}{10^{2017}^{ }+1}\)
Anh hiền àaaaaaaaaaaaaaaaaaaaaaaaaa
Ta có công thức :
\(\frac{a}{b}>\frac{a+c}{b+c}\) \(\left(\frac{a}{b}>1;a,b,c\inℕ^∗\right)\)
Áp dụng vào ta có :
\(B=\frac{10^{2018}+1}{10^{2017}+1}>\frac{10^{2018}+1+9}{10^{2018}+1+9}=\frac{10^{2018}+10}{10^{2018}+10}=\frac{10\left(10^{2017}+1\right)}{10\left(10^{2016}+1\right)}=\frac{10^{2017}+1}{10^{2016}+1}=A\)
\(\Rightarrow\)\(B>A\) hay \(A< B\)
Vậy \(A< B\)
Chúc bạn học tốt ~
So sánh A=\(\frac{10^{2017}+1}{10^{2018}+1}\), B=\(\frac{10^{2016}+1}{10^{2017}+1}\)