Question 432440
To rationalize the denominator means to eliminate the radicals on denominator.
For this reason we multiply the numerator and denominator with the conjugate of denominator, which in our case is: 

{{{sqrt(7)-sqrt(3)}}}

 {{{y(sqrt(7)-sqrt(3))/(sqrt(7)+sqrt(3))(sqrt(7)-sqrt(3))}}}=    (simplify).

{{{(y*sqrt(7)-y*sqrt(3))/(7-3)=(y*sqrt(7)-y*sqrt(3))/4}}}

To find this result we apply on the denominator the algebraic formula:

{{{(a+b)(a-b)=a^2-b^2}}}.