so sánh A và B với A= 2024^3 và B =2023.2024.2025
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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
\(A=\dfrac{2024^{2023}+1}{2024^{2024}+1}\)
\(2024A=\dfrac{2024^{2024}+2024}{2024^{2024}+1}=\dfrac{\left(2024^{2024}+1\right)+2023}{2024^{2024}+1}=\dfrac{2024^{2024}+1}{2024^{2024}+1}+\dfrac{2023}{2024^{2024}+1}=1+\dfrac{2023}{2024^{2024}+1}\)
\(B=\dfrac{2024^{2022}+1}{2024^{2023}+1}\)
\(2024B=\dfrac{2024^{2023}+2024}{2024^{2023}+1}=\dfrac{\left(2024^{2023}+1\right)+2023}{2024^{2023}+1}=\dfrac{2024^{2023}+1}{2024^{2023}+1}+\dfrac{2023}{2024^{2023}+1}=1+\dfrac{2023}{2024^{2023}+1}\)
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: \(B=\dfrac{154}{155+156}+\dfrac{155}{155+156}\)
\(\dfrac{154}{155}>\dfrac{154}{155+156}\)
\(\dfrac{155}{156}>\dfrac{155}{155+156}\)
=>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, A = 3020 xx 3110 - 5 = 3020 xx 3109 + 3020 - 5`
`= 3020 xx 3109 + 3015 = B`.
`b, B = (2022-2)(2022+2) = 2022^2-4 < 2022^2 = A.`
\(A=\dfrac{10^{2024}+1}{10^{2023}+1}=\dfrac{10\left(10^{2023}+1\right)}{10^{2023}+1}-\dfrac{9}{10^{2023}+1}=1-\dfrac{9}{10^{2023}+1}\)
\(B=\dfrac{10^{2023}+1}{10^{2022}+1}=\dfrac{10\left(10^{2022}+1\right)}{10^{2022}+1}-\dfrac{9}{10^{2022}+1}=1-\dfrac{9}{10^{2022}+1}\)
Vì \(\dfrac{9}{10^{2023}+1}< \dfrac{9}{10^{2022}+1}\)
\(\Rightarrow A>B\)
\(a,\dfrac{1}{2023}>0;-\dfrac{5}{2024}< 0\\ Nên:-\dfrac{5}{2024}< 0< \dfrac{1}{2023}\Rightarrow-\dfrac{5}{2024}< \dfrac{1}{2023}\\ b,\dfrac{678}{876}< 1;\dfrac{987}{789}>1\\ Nên:\dfrac{678}{876}< 1< \dfrac{987}{789}\Rightarrow\dfrac{678}{876}< \dfrac{987}{789}\)
\(c,\dfrac{535353}{585858}=\dfrac{535353:10101}{585858:10101}=\dfrac{53}{58}=1-\dfrac{5}{58}\\ \dfrac{301}{306}=1-\dfrac{5}{306}\\ Vì:\dfrac{5}{58}>\dfrac{5}{306}\Rightarrow1-\dfrac{5}{58}< 1-\dfrac{5}{306}\\ Nên:\dfrac{535353}{585858}< \dfrac{301}{306}\)
\(d,\dfrac{9}{71}=\dfrac{9.3}{71.3}=\dfrac{27}{213}\\ Vì:\dfrac{27}{213}< \dfrac{27}{211}\\ Nên:\dfrac{9}{71}< \dfrac{27}{211}\)
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
B = \(1-\dfrac{1}{2025}\) \(A=1-\dfrac{1}{2024}\)
Vì \(\dfrac{1}{2025}< \dfrac{1}{2024}\)
Nên B>A
Ta có :
\(\dfrac{2023}{2024}\)=\(\dfrac{2024-1}{2024}\)=\(\dfrac{2024}{2024}\)-\(\dfrac{1}{2024}\)=1-\(\dfrac{1}{2024}\)
\(\dfrac{2024}{2025}\)=\(\dfrac{2025-1}{2025}\)=\(\dfrac{2025}{2025}\)-\(\dfrac{1}{2025}\)=1=\(\dfrac{1}{2025}\)
Ta thấy: \(\dfrac{1}{2024}\) lớn hơn \(\dfrac{1}{2025}\)
Nên : \(\dfrac{2023}{2024}\) lớn hơn \(\dfrac{2024}{2025}\)
⇒A lớn hơn B

2023.2025 = (2024 - 1).(2024 + 1)
2023.2025 = 2024.2024 + 2024 - 20224 - 1
2023.2025 = 2024.2024 - 1 < 2024^2
2023.2024.2025 < 2024^2.2024 = 2024^3
A > B
Ta có
A = 2024³
B = 2023 · 2024 · 2025
Nhận xét:
2023 = 2024 − 1
2025 = 2024 + 1
⇒ B = (2024 − 1) · 2024 · (2024 + 1)
Áp dụng hằng đẳng thức:
(x − 1)(x + 1) = x² − 1
⇒ B = 2024(2024² − 1)
= 2024³ − 2024
So sánh với A:
A = 2024³
⇒ A − B = 2024³ − (2024³ − 2024)
= 2024 > 0
Vậy A > B.