2 câu trả lời
$\sqrt{28}$ + 2$\sqrt{63}$ -5$\sqrt{18}$ + $\sqrt{72}$
= 2$\sqrt{7}$+2.3$\sqrt{7}$-5.3$\sqrt{2}$+6$\sqrt{2}$
=2$\sqrt{7}$+6$\sqrt{7}$-15$\sqrt{2}$+6$\sqrt{2}$
=8$\sqrt{7}$-9$\sqrt{2}$
$\sqrt{28}$ + 2$\sqrt{63}$ -5$\sqrt{18}$ + $\sqrt{72}$
= 2$\sqrt{7}$+2.3$\sqrt{7}$-5.3$\sqrt{2}$+6$\sqrt{2}$
=2$\sqrt{7}$+6$\sqrt{7}$-15$\sqrt{2}$+6$\sqrt{2}$
=8$\sqrt{7}$-9$\sqrt{2}$