Ответ:

Объяснение:

√12 ·√12=12^(1/2) ·12^(1/2)=12^(1/2 +1/2)=12^(2/2)=12¹=12

√63 ·√7=√(7·9) ·√7=3·7^(1/2) ·7^(1/2)=3·7^(1/2 +1/2)=3·7^(2/2)=3·7=21