Question

http://i.imgur.com/lziFe7N.png
i forgot how to work this out??

Answer 1

you can write \[ \sqrt{a\cdot b}= \sqrt{a} \cdot \sqrt{b} \]
and vice versa
in other words, you can multiply the square root part. what do you get ?

Answer 2

@phi
i got 5.6637

Answer 3

Without estimating, try using Phi's method:

\(\Large 6\sqrt{7}*2\sqrt{21} \)

\(\Large 6\sqrt{7}*2\sqrt{7*3} \)

\(\Large (6*2)\sqrt{\color{red}{7*7}*3} \)

When there is a perfect square, you are allowed to remove it:

\(\Large (6*2*7)\sqrt{3} \)

Answer 4

ohh thanks
sorry im so bad at this lol