Given the expression:
[tex]\sqrt[]{-3}\cdot\sqrt[]{12}[/tex]You need to remember the following property:
[tex]\sqrt[n]{b^{}}\cdot\sqrt[n]{a}=\sqrt[n]{ba}[/tex]Where "n" is the index of the root and "b" and "a" are Radicands.
Then, since the roots given in the exercise are the same, you can multiply the Radicands:
[tex]=\sqrt[]{(-3)(12)}=\sqrt[]{-36}[/tex]Notice that the number inside the square root is negative. Then, you need to remember the following:
[tex]\sqrt[]{-1}=i[/tex]Therefore, in order to simplify it, you need to take the square root of 36 and write the Imaginary Unit "i" next to it:
[tex]=6i[/tex]Hence, the answer is:
[tex]=6i[/tex]