Question 110630
Not sure if your problem is {{{4/sqrt(5)+sqrt(2)}}} or {{{4/(sqrt(5)+sqrt(2))}}}
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I'm also not sure what you want to do with this expression, but I'll assume that you want to rationalize the denominator.
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Let's try the second expression first.  In order to rationalize (get the radicals out of) a denominator that is the sum (or difference) of two radicals, you need to remember the factoring rule for the difference of two squares.
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{{{a^2-b^2=(a+b)(a-b)}}}
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{{{(sqrt(5)+sqrt(2))(sqrt(5)-sqrt(2))=(sqrt(5))^2-(sqrt(2))^2=5-2=3}}}
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3 is a nice neat rational denominator, so all we have to do is multiply the expression by 1, in the form of {{{(sqrt(5)-sqrt(2))/(sqrt(5)-sqrt(2))}}}
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{{{(4/(sqrt(5)+sqrt(2)))((sqrt(5)-sqrt(2))/(sqrt(5)-sqrt(2)))}}}
{{{(4/3)(sqrt(5)-sqrt(2))}}}
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If the problem is actually the first expression, then you need to multiply the first term by 1 in the form of {{{sqrt(5)/sqrt(5)}}}, thus:
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{{{(4/sqrt(5))(sqrt(5)/sqrt(5))+sqrt(2)}}} 
{{{(4sqrt(5)/5)+sqrt(2)}}}, then find a common denominator and add:
{{{(4sqrt(5)+5sqrt(2))/5}}}
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Hope that helps.