The Laplace transform of sgn [t(t2 – 9)] is ______.
1
\(2\left( {\frac{{{e^{ - 3s}}}}{s} - \frac{1}{s}} \right)\)
2
\(\left( {\frac{2}{s} - \frac{{{e^{ - 3s}}}}{s}} \right)\)
3
\(2\left( {\frac{{{e^{3s}}}}{s} + \frac{{{e^{ - 3s}}}}{s}} \right)\)
4
does not exist