Question 359606
{{{ (2sqrt(3)-4sqrt(6))(3sqrt(3)+6sqrt(6)) }}}
= {{{6*3 - 24*6 + 12sqrt(18) - 12sqrt(18)}}}
= {{{18 - 144}}}
= -126
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You're way off.
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Or do it this way:
{{{ (2sqrt(3)-4sqrt(6))(3sqrt(3)+6sqrt(6)) }}}
= {{{2*(sqrt(3) - 2sqrt(6)) * 3*(sqrt(3) - 2sqrt(6))}}}
= {{{6* (sqrt(3) - 2sqrt(6)) * (sqrt(3) - 2sqrt(6))}}}
= 6 * (3 - 24)
= -126