so sánh A=2020^2018-1/2020^2019-2019 với B=2020^2019-1/2020^2020+2019 30/10/2021 Bởi Alexandra so sánh A=2020^2018-1/2020^2019-2019 với B=2020^2019-1/2020^2020+2019
Có phải đề thế này ko: A$=\frac{2020^{2018}-1}{2020^{2019}-2019}$ A$=\frac{2020^{2018}-1}{2020^{2018}.2020-2019}$ A$=\frac{1}{2020-2019}$ A$=1$ B$=\frac{2020^{2019}-1}{2020^{2020}-2019}$ B$=\frac{2020^{2019}-1}{2020^{2019}.2020-2019}$ B$=1$ Bình luận
Ta có: ` A = \frac{2020^{2018}-1}{2020^{2019}-2019} ` ` <=> 2020A = \frac{2020^{2019} – 2020}{2020^{2019} – 2019} ` ` B = \frac{2020^{2019}-1}{2020^{2020}+2019} ` ` <=> 2020B = \frac{2020^{2020}-2020}{2020^{2020}+2019} ` Do: ` 2020^{2019} – 2019 < 2020^{2020} + 2019 ` ` => \frac{2020^{2019} – 2020}{2020^{2019} – 2019} > \frac{2020^{2020}-2020}{2020^{2020}+2019} ` ` => 2020A > 2020B ` ` => A > B ` Bình luận
Có phải đề thế này ko:
A$=\frac{2020^{2018}-1}{2020^{2019}-2019}$
A$=\frac{2020^{2018}-1}{2020^{2018}.2020-2019}$
A$=\frac{1}{2020-2019}$
A$=1$
B$=\frac{2020^{2019}-1}{2020^{2020}-2019}$
B$=\frac{2020^{2019}-1}{2020^{2019}.2020-2019}$
B$=1$
Ta có:
` A = \frac{2020^{2018}-1}{2020^{2019}-2019} `
` <=> 2020A = \frac{2020^{2019} – 2020}{2020^{2019} – 2019} `
` B = \frac{2020^{2019}-1}{2020^{2020}+2019} `
` <=> 2020B = \frac{2020^{2020}-2020}{2020^{2020}+2019} `
Do: ` 2020^{2019} – 2019 < 2020^{2020} + 2019 `
` => \frac{2020^{2019} – 2020}{2020^{2019} – 2019} > \frac{2020^{2020}-2020}{2020^{2020}+2019} `
` => 2020A > 2020B `
` => A > B `