Posted by Nancy on Tuesday, April 17, 2012 at 12:36am.
3√(63x^5/(72y^6))
=3√9 √7 x^2 √x/(√36 √2 y^3)
= 9x^2√(7x) / (6√2 y^3)
= 3x^2 √(7x) / (2√2y^3)
they might now multiply top and bottom by √2 to rationalize the denominator to get
3x^2√(14x) / (4y^3)
check my work, I should have written it down first.