a) √6*√5=√(6*5)=√30; √7*√12=√(7*12)=√84; √15*√3=√(3*5*3)=3√5;
√3*√24=√(3*24)=√{[(3*3)*(2*2)]*2}=[tex]sau= \sqrt{9*4*2}=3*2 \sqrt{2}=6 \sqrt{2} [/tex] √6*√14=√(6*14)=[tex] \sqrt{2*3*2*7}= \sqrt{4*3*7}= \sqrt{4} \sqrt{3*7}=2 \sqrt{21} [/tex]
b) √7*√13=√(7*13)=√91; √2*√19=√38; √6*√11=√66; √13*√7=√(13*7)=√91
