Question 236387
(3 sqrt 3 - 9 sqrt 6) 
(2 sqrt 3 - 6 sqrt 6) I'll assume it's -6 not +6.
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6*3-18sqrt18-18sqrt18+54*6
18-36sqrt18+324
342-36sqrt(9*2)
342-36*3sqrt2
342-108sqrt2 ans.
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(3 sqrt 3 - 9 sqrt 6) 
(2 sqrt 3 + 6 sqrt 6) if it is a +6 then:
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6*3-18sqrt18+18sqrt18-54*6
18-324=-306 ans.