Question 750938
<pre>
&#8730;<span style="text-decoration: overline">3x</span>·&#8730;<span style="text-decoration: overline">51x</span>

Break the 51 down to 3·17

&#8730;<span style="text-decoration: overline">3x</span>·&#8730;<span style="text-decoration: overline">3·17x</span>

Multiply under the radicals:

&#8730;<span style="text-decoration: overline">3·3·17x²</span>

&#8730;<span style="text-decoration: overline">3²·17x²</span>

Take out 3² as just a 3 in front of the radical.
Take out x² as just as |x| in front of the radical.
We must put the x between absolute value bars because the 
original problem is the product of two radical square roots,
which are never negative, therefore the answer cannot be negative.
But x is a variable so it might be negative. So to assure that the
answer is not negative we must put absolute value bars around
x.

Answer:

3|x|&#8730;<span style="text-decoration: overline">17</span>

Edwin</pre>