Hãy giúp tôi:
so sánh ko quy đồng :
a, 15/59 và 17/69 b, 2023/2022 và 2025/2024
c, 1313/1717 và 212121/252525
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\(A=2023\times2024\\ =\left(2022+1\right)\times2024\\ =2022\times2024+2024\\ B=2022\times2025\\ =2022\times\left(2024+1\right)\\ =2022\times2024+2022\)
Vì 2022 x 2024 = 2022 x 2024
=> 2024 > 2022
=> A> B
Cách 2
A= 2023 x 2024 = 4094552
B = 2022 x 2025 =4094550
Vì 4094552 > 4094550 = > A> B
a: \(B=\dfrac{154}{155+156}+\dfrac{155}{155+156}\)
\(\dfrac{154}{155}>\dfrac{154}{155+156}\)
\(\dfrac{155}{156}>\dfrac{155}{155+156}\)
=>154/155+155/156>(154+155)/(155+156)
=>A>B
b: \(C=\dfrac{2021+2022+2023}{2022+2023+2024}=\dfrac{2021}{6069}+\dfrac{2022}{6069}+\dfrac{2023}{6069}\)
2021/2022>2021/6069
2022/2023>2022/2069
2023/2024>2023/6069
=>D>C
\(A=\dfrac{2024^{2023}+1}{2024^{2024}+1}\)
\(2024A=\dfrac{2024^{2024}+2024}{2024^{2024}+1}=\dfrac{\left(2024^{2024}+1\right)+2023}{2024^{2024}+1}=\dfrac{2024^{2024}+1}{2024^{2024}+1}+\dfrac{2023}{2024^{2024}+1}=1+\dfrac{2023}{2024^{2024}+1}\)
\(B=\dfrac{2024^{2022}+1}{2024^{2023}+1}\)
\(2024B=\dfrac{2024^{2023}+2024}{2024^{2023}+1}=\dfrac{\left(2024^{2023}+1\right)+2023}{2024^{2023}+1}=\dfrac{2024^{2023}+1}{2024^{2023}+1}+\dfrac{2023}{2024^{2023}+1}=1+\dfrac{2023}{2024^{2023}+1}\)
Vì \(2024>2023=>2024^{2024}>2024^{2023}\)
\(=>2024^{2024}+1>2024^{2023}+1\)
\(=>\dfrac{2023}{2024^{2023}+1}>\dfrac{2023}{2024^{2024}+1}\)
\(=>A< B\)
\(#PaooNqoccc\)
a) \(2023^{2024}\) và \(2023^{2023}\)
vì 2024 > 2023 nên 20232024 > 20232023
Vậy 20232024 > 20232023
b) \(17^{2024}\) và \(18^{2024}\)
vì 17 < 18 nên 172024 < 18 2024
Vậy 172024 < 182024
So sánh
A = \(\dfrac{2022^{2023}+1}{2022^{2024}+1}\) và B = \(\dfrac{2022^{2022}+1}{2022^{2023}+1}\)
Trước hết ta phải chứng minh \(\dfrac{a}{b}< \dfrac{a+1}{b+1}\) (a, b ϵ N; a < b).
Thật vậy, \(\dfrac{a}{b}=\dfrac{a\left(b+1\right)}{b\left(b+1\right)}=\dfrac{a+ab}{b^2+b}\) và \(\dfrac{a+1}{b+1}=\dfrac{\left(a+1\right)b}{\left(b+1\right)b}=\dfrac{ab+b}{b^2+b}\).
Mà theo giả thuyết là a < b nên \(\dfrac{a+ab}{b^2+b}< \dfrac{ab+b}{b^2+b}\), suy ra \(\dfrac{a}{b}< \dfrac{a+1}{b+1}\) (a, b ϵ N; a < b).
Từ đây ta có:
\(B=\dfrac{2022^{2022}+1}{2022^{2023}+1}=\dfrac{2022^{2023}+2022}{2022^{2024}+2022}=\dfrac{2022^{2023}+2021+1}{2022^{2024}+2021+1}\)
Đặt \(A_1=\dfrac{2022^{2023}+2}{2022^{2024}+2}=\dfrac{2022^{2023}+1+1}{2022^{2024}+1+1}\), rõ ràng \(A_1>A\).
Đặt \(A_2=\dfrac{2022^{2023}+3}{2022^{2024}+3}=\dfrac{2022^{2023}+2+1}{2022^{2024}+2+1}\), rõ ràng \(A_2>A_1\).
...
Đặt \(A_{2020}=\dfrac{2022^{2023}+2021}{2022^{2024}+2021}=\dfrac{2022^{2023}+2020+1}{2022^{2024}+2020+1}\), rõ ràng \(A_{2020}>A_{2019}\) và \(B>A_{2020}\).
Suy ra \(B>A_{2020}>A_{2019}>...>A_2>A_1>A\). Vậy A < B.
Ta có A = \(\dfrac{2022^{2023}}{2022^{2024}}=\dfrac{1}{2022}\) ; B = \(\dfrac{2022^{2022}}{2022^{2023}}=\dfrac{1}{2022}\)
Mà \(\dfrac{1}{2022}=\dfrac{1}{2022}\)
Vậy A = B
\(\dfrac{1313}{1717}=\dfrac{101x13}{101x17}=\dfrac{13}{17}\)
\(\dfrac{131313}{171717}=\dfrac{10101x13}{10101x17}=\dfrac{13}{17}\)
Vậy \(\dfrac{1313}{1717}=\dfrac{131317}{171717}\)
\(\dfrac{1313}{1717}và\dfrac{131313}{171717}\\ \dfrac{1313}{1717}=\dfrac{13}{17}\\ \dfrac{131313}{171717}=\dfrac{13}{17}\\ \Rightarrow\dfrac{1313}{1717}=\dfrac{131313}{171717}\)
Lời giải:
a.
$\frac{15}{59}> \frac{15}{60}=\frac{1}{4}=\frac{17}{68}> \frac{17}{69}$
b.
$\frac{2023}{2022}=1+\frac{1}{2022}> 1+\frac{1}{2024}=\frac{2025}{2024}$
c.
$\frac{1313}{1717}=\frac{1313:101}{1717:101}=\frac{13}{17}=1-\frac{4}{17}< 1-\frac{4}{25}=\frac{21}{25}$
$\frac{212121}{252525}=\frac{212121:10101}{252525:10101}=\frac{21}{25}$
$\Rightarrow \frac{131313}{171717}< \frac{212121}{252525}$