Question

(√63-2√28+3√7).√7

Answer 1

\(\left(\sqrt{63}-2\sqrt{28}+3\sqrt{7}\right)\cdot\sqrt{7}\\ =\left(\sqrt{9\cdot7}-2\sqrt{4\cdot7}+3\sqrt{7}\right)\cdot\sqrt{7}\\ =\left(3\sqrt{7}-4\sqrt{7}+3\sqrt{7}\right)\cdot\sqrt{7}\\ =3\cdot7-4\cdot7+3\cdot7\\ =21-28+21\\ =14\)

Answer 2

ấn chữ M ngược cho dễ hiểu

 

Answer 3

(3\(\sqrt{7}\)-\(4\sqrt{7}\)+3\(\sqrt{7}\))*\(\sqrt{7}\)
2\(\sqrt{7}\)*\(\sqrt{7}\)=14