Ответы и объяснения

2013-04-19T14:55:30+04:00

(7-sqrt{189}-sqrt{21}-9/-20)*(1-2sqrt{21})=(-2-3sqrt{21}-sqrt{21}/-20)*(1-2sqrt{21})= (-2(1+2sqrt{21}/-20)*(1-2sqrt{21})=(1+2sqrt{21}/10)*(1-2sqrt{21})=1-84/10=-8.3