This is so confusing (8 + sqrt of -18) - (4 + 3 sqrt of 2i)
Last edited by mr fantastic; Sep 14th 2009 at 05:51 AM. Reason: Changed post title and removed extraneous o's from so.
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Originally Posted by tsmith This is soooooo confusing (8 + sqrt of -18) - (4 + 3 sqrt of 2i) Is it $\displaystyle (8+\sqrt{-18})-(4+3\sqrt{2}i)$? If so, note that $\displaystyle \sqrt{-18}=\sqrt{9(-2)}=3\sqrt{-2}=3\sqrt{2}i$ Now simplify $\displaystyle 8+3\sqrt{2}i-4-3\sqrt{2}i$ by combining the real and imaginary parts. Can you continue from here?
So the 3 sqrt 2i will cancel each other out, right? So the answer would be 4?
Originally Posted by tsmith So the 3 sqrt 2i will cancel each other out, right? So the answer would be 4? yes.
That is, assuming you meant $\displaystyle 4+ 3i\sqrt{2}$ and not $\displaystyle 4+ 3\sqrt{2i}$. Not being able to tell is that "i" is inside or outside the square root is a good reason to always write "i" in front of square roots, not behind them.
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