Break those numbers down into prime factors using factor trees:
726 252 63
/ \ / \ /\
2 263 2 126 9 7
/ \ / \ / \
3 121 2 63 3 3
/ \ /\
11 11 7 9
/ \
3 3
726 = 2·3·11², 252 = 2²·3²·7 63 = 3²·7
Take all the numbers with squares out from under the radical and place
the numbers without the squares out in front of the radicals:
comes out of the first radical as a 11 muiltiplied in front.
Both and come out from under the radical in the second
radical, as a 2 multiplied by a 3 in front of the second radical:
The 2nd and 3rd terms cancel and you're only left with the fitst term:
Edwin