随机变量\(X\)的分布列如表所示,若\(E(x)=\dfrac{1}{3}\),则\(D(3x-2)=(\) \()\)
\(X\)
\(-1\)
\(0\)
\(1\)
\(P\)
\(\dfrac{1}{6}\)
\(a\)
\(b\)
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