Question

Помогите пожалуйста

Answer 1

1) $( sqrt{5} - sqrt{18} )( sqrt{5}-2 sqrt{2} )= ( sqrt{5}- sqrt{9*2} )( sqrt{5} - 2 sqrt{2} )=( sqrt{5}-3 sqrt{2})( sqrt{5}$$2 sqrt{2}) = sqrt{5} * sqrt{5} - sqrt{5} *2 sqrt{2} -3 sqrt{2} * sqrt{5}+3 sqrt{2}*2 sqrt{2}=5 - 2 sqrt{10}-$$3 sqrt{10} +12=17-5 sqrt{10}$
2) $(2 sqrt{7}+ sqrt{12} )( sqrt{12}- sqrt{7}) - sqrt{84}=(2 sqrt{7}+ sqrt{4*3})( sqrt{4*3} - sqrt{7})-$$sqrt{4*21} =(2 sqrt{7} +2 sqrt{3})(2 sqrt{3} - sqrt{7})-2 sqrt{21}=4 sqrt{21} -14+12-2 sqrt{21} -$$2 sqrt{21}=- 2$