Posted by **mada** on Tuesday, April 6, 2010 at 10:44pm.

(3+4i)(3-4i)

- algebra maginary numbers -
**Reiny**, Tuesday, April 6, 2010 at 11:27pm
just expand it as if the i was a variable

(3+4i)(3-4i)

= 9 - 12i + 12i -12i^2, now remember i^2 = -1

= 9 - 12(-1)

= 9+12

= 21

- algebra maginary numbers -
**mada**, Tuesday, April 6, 2010 at 11:33pm
wait when you factor it wouldnt it be 9-12i+12i-16i^2

- algebra maginary numbers -
**Reiny**, Tuesday, April 6, 2010 at 11:36pm
of course, my silly error

- algebra maginary numbers -
**mada**, Tuesday, April 6, 2010 at 11:41pm
its totally cool you have helped alot :)

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