Với mọi \(n\in N\)*, đẳng thức nào sau đây đúng?
\(2+5+8+...+\left(3n-1\right)=\dfrac{n\left(3n+1\right)}{2}\).\(2+5+8+...+\left(3n-1\right)=\dfrac{n\left(3n-1\right)}{2}\).\(1+3+5+7+...+\left(2n-1\right)=\dfrac{n\left(3n-1\right)}{2}\).\(2^2+5^2+8^2+...+\left(3n-1\right)^2=\dfrac{n\left(3n+1\right)^2}{2}\).