Question

I need help for algebra 2 for simplify form for example (3x-2i)(3x+2i)

Answer 1

$(a+b)(a-b)=a^2-b^2\\\\ (3x-2i)(3x+2i)=\\ 9x^2-4i^2\\ \\ i=\sqrt{-1}\\ i^2=-1\\ \\ 9x^2-4\cdot (-1)=9x^2+4$

Answer 2

Let's start...

$(3x-2i)*(3x+2i)$

$3x*3x+3x*2i-2i*3x-2i*2i$

$9x^2+6xi-6xi-4i^2$

$9x^2-4i^2$

we don't finish it yet...

$i^2=-1$

Let's replace it

$9x^2-4*(-1)$

$\boxed{\boxed{9x^2+4}}$