[tex]4 \sqrt{5} \times 3 = 4 \sqrt{5 \times 3 } = 4 \sqrt{15} \\ \\ - 3 \sqrt{2} \times 4 \sqrt{7} = - 3 \times 4 \sqrt{2 \times 7} = \\ = - 12 \sqrt{14} \\ [/tex]
[tex] - 2 \sqrt{7} \times - 3 \sqrt{3} = - 2 \times ( - 3) \sqrt{7 \times 3} = \\ = 6 \sqrt{21} [/tex]
a✓b • c✓d = a•c ✓b•d
