Bài này mình nghĩ chắc là dấu trừ. Nếu cộng thì thế nào

2022.20212021 + 2021.20222022

=2022.2021.10001+2021.2022.10001

=2.2022.2021.1001

Nếu trừ thì thế này:

2022.20212021 - 2021.20222022

=2022.2021.10001 - 2021.2022.10001

=0

a) \(\dfrac{5}{4}+\left(2x-\dfrac{1}{2}\right)=\dfrac{5}{6}\Leftrightarrow2x-\dfrac{1}{2}=-\dfrac{5}{12}\)

\(\Leftrightarrow2x=\dfrac{1}{12}\Leftrightarrow x=\dfrac{1}{24}\)

Vậy \(x=\dfrac{1}{24}\)

b)\(\dfrac{3}{2}-\left(x+\dfrac{1}{4}\right)=\dfrac{5}{8}\Leftrightarrow x+\dfrac{1}{4}=\dfrac{7}{8}\)

\(\Leftrightarrow x=\dfrac{5}{8}\)

Vậy \(x=\dfrac{5}{8}\)

c)\(\dfrac{x}{3}=\dfrac{12}{x}\Rightarrow x^2=36\Leftrightarrow x=\pm\sqrt{36}\)\(\Leftrightarrow x=\pm6\)( thoả mãn \(x\ne0\))

Vậy \(x=\pm6\)