Answer :

D3xt3R
Let's start...

[tex](3x-2i)*(3x+2i)[/tex]

[tex]3x*3x+3x*2i-2i*3x-2i*2i[/tex]

[tex]9x^2+6xi-6xi-4i^2[/tex]

[tex]9x^2-4i^2[/tex]

we don't finish it yet...

[tex]i^2=-1[/tex]

Let's replace it

[tex]9x^2-4*(-1)[/tex]

[tex]\boxed{\boxed{9x^2+4}}[/tex]
tomek1172
[tex](a+b)(a-b)=a^2-b^2\\\\ (3x-2i)(3x+2i)=\\ 9x^2-4i^2\\ \\ i=\sqrt{-1}\\ i^2=-1\\ \\ 9x^2-4\cdot (-1)=9x^2+4[/tex]

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