Question 201162
I assume the problem is to rationalize {{{-sqrt(245x^3/(y^5))}}}
If this is correct, then the denominator of fraction needs to be a perfect square. Since a variable raised to an even power is a perfect square, the current denominator, y^5, is not a perfect square. The simplest way to make the exponent on y even is to multiply y^5 by y which results in y^6. 

The only valid way to multiply the denominator by y is to multiply the numerator by y, also:
{{{-sqrt((245x^3/y^5)*(y/y))}}}
which results in:
{{{-sqrt(245x^3y/y^6))}}}
Now you can split the square root of the fraction into a fraction of square roots:
{{{-(sqrt(245x^3y)/sqrt(y^6))}}}
The denominator, {{{sqrt(y^6)}}}, will simplify to y^3 making the answer:
{{{-(sqrt(245x^3y)/(y^3))}}}