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If $f\left( x \right) ={ x }^{ 4 }{ e }^{ x }$, then $f^{ \prime \prime }\left( x \right) =$

$12{ x }^{ 2 }{ e }^{ x }$

${ x }^{ 4 }{ e }^{ x }+4{ x }^{ 3 }{ e }^{ x }$

${ x }^{ 4 }{ e }^{ x }+4{ x }^{ 3 }{ e }^{ x }+12{ x }^{ 2 }{ e }^{ x }$

${ x }^{ 4 }{ e }^{ x }+8{ x }^{ 3 }{ e }^{ x }+12{ x }^{ 2 }{ e }^{ x }$