Question 37748
When adding and subtracting radical expressions we first need to simplify...
{{{ -4 *sqrt(25n) + 2* sqrt(81n) + sqrt(700n) }}}
(from left to right)
The square root of 25 is 5 so the first expression can be simplified as...
{{{ -4*5*sqrt (n)}}}={{{ -20*sqrt (n)}}}
Then, in the second expression the square root of 81 = 9 which can be simplified as...
{{{ 2*9*sqrt(n) }}}={{{ 18*sqrt(n) }}}
And in the third expression 700 = 7 * 100, and 100 12 equal to {{{10^2}}}
So it can be simplified as...
{{{ 10*sqrt(7n) }}}
So if we put the three expressions back into the equation we get...
{{{ -20*sqrt (n) + 18*sqrt(n) + 10*sqrt(7n)}}}
Now we can combine like terms.
Remember that we can only add and subtract radical expression that contain the same base and index.
So...
{{{ -20*sqrt (n) + 18*sqrt(n) + 10*sqrt(7n)}}}={{{-2*sqrt (n) + 10*sqrt (7n)}}} 
And...
{{{-2*sqrt (n) + 10*sqrt (7n)}}} 
Is the most this problem can be simplified.
I hope this helps!
Good Luck!