`\color{#c1b1fa}{t}\color{#b6b1fa}{h}\color{#b1bafa}{u}\color{#b1c4fa}{y}\color{#b1d1fa}{h}\color{#b1d9fa}{i}\color{#b1dffa}{e}\color{#b1eafa}{n}\color{#b1f2fa}{3}\color{#b1fafa}{6}\color{#b1faf2}{i}\color{#b1f2fa}{n}\color{#b1eafa}{n}`

`A = 1 + 4 + 4^2 + ... + 4^2021`

`4A = 4 + 4^2 + 4^3 + ... + 4^2022`

`4A - A = (4 + 4^2 + 4^3 + ... + 4^2022) - (1 + 4 + 4^2 + ... + 4^2021)`

`3A =4^2022 - 1`

`3A = (2^2)^2022 - 1`

`3A = 2^4044 - 1`

Vì: `2^4044 - 1 < 2^4044`

`=> 3A < 2^4044`

Vậy `3A < 2^4044`