Với mọi số tự nhiên \(n\ge1\), đẳng thức nào sau đây đúng?
\(1^2+2^2+3^2+...+\left(n-1\right)^2+n^2=\dfrac{n\left(n+1\right)\left(2n+1\right)}{6}\).\(1^2+2^2+3^2+...+\left(n-1\right)^2+n^2=\dfrac{n\left(n+1\right)\left(2n+1\right)}{3}\).\(1^2+2^2+3^2+...+\left(n-1\right)^2+n^2=\dfrac{n\left(n+1\right)\left(2n+1\right)}{9}\).\(1^2+2^2+3^2+...+\left(n-1\right)^2+n^2=\dfrac{n\left(n+1\right)\left(2n+1\right)}{8}\).