# square root question

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• January 10th 2009, 01:42 PM
netlab
square root question
Good Day,

Just wanted to ensure i did this question correctly, the question was to write the problem below in standard form. If incorrect any help to solve this question would be appreciated.

http://img176.imagevenue.com/loc10/t...d_122_10lo.jpg

thanks in advance
• January 10th 2009, 02:50 PM
Soroban
Hello, netlab!

Your steps seem to be okay, but that $\sqrt{1}$ is unnecessary.

$5\sqrt{\text{-}16} \:+ \:3\sqrt{\text{-}81}$

. . $= \;5\sqrt{(16)(\text{-}1)} \:+ \:3\sqrt{(81)(\text{-}1)}$

. . $= \;5\!\cdot\!\sqrt{16}\!\cdot\!\sqrt{\text{-}1} \:+ \:3\!\cdot\!\sqrt{81}\!\cdot\!\sqrt{\text{-}1}$

. . $= \;5\!\cdot\!4\!\cdot\!i \:+\: 3\!\cdot\!9\!\cdot\!i$

. . $=\;\;20i + 27i \;\;=\;\;\boxed{47i}$

• January 10th 2009, 04:02 PM
netlab
Ok, thanks a lot for your help