Answer:
[tex]4\sqrt{-2}[/tex]
Step-by-step explanation:
We can write the expression [tex]\sqrt{-18}[/tex] in another form, by decomposing the number 18.
[tex]\sqrt{-18}=\sqrt{9(-2)}=\sqrt{(3^{2})( -2)} =3\sqrt{-2}[/tex]
Since the two terms have the same radicand, we can make the sum of the coefficients.
[tex]\sqrt{-2}+3\sqrt{-2}=4\sqrt{-2}[/tex]
we can also express this number as
[tex]4\sqrt{-2}=\sqrt{-32}=4\sqrt{2}i[/tex]
