How do you simplify #(3 + 4i)(3 - 4i)#?

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Answer 1 · 2016-02-12T10:46:49

25

Given:#" "(3+4i)(3-4i)#

I notice that this is our good old friend of

#" "(a^2-b^2)=(a-b)(a+b)#

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Write as:#" "3^2-(4i)^2#

#=9-(16i^2)#

But #" "i^2=-1# giving:

#=9+16 =25#