Accepted Answer
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]
Suggested Answer
[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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