Question

Answer 1

6:

a: \(=\dfrac{20\cdot2\sqrt{3}-15\cdot3\sqrt{3}}{5\sqrt{3}}=\dfrac{40\sqrt{3}-45\sqrt{3}}{5\sqrt{3}}\)

\(=-\dfrac{5\sqrt{3}}{5\sqrt{3}}=-1\)

b: \(=\dfrac{5\sqrt{3}+9\sqrt{3}-4\sqrt{3}}{\sqrt{3}}=5+9-4=10\)

c: \(\left(\sqrt{2}+1\right)^2+\left(\sqrt{2}-1\right)^2\)

\(=3+2\sqrt{2}+3-2\sqrt{2}\)

=6

d: \(=\left(2\sqrt{7}-2\sqrt{3}+\sqrt{7}\right)\cdot\sqrt{7}+2\sqrt{21}\)

\(=\left(3\sqrt{7}-2\sqrt{3}\right)\cdot\sqrt{7}+2\sqrt{21}\)

\(=21-2\sqrt{21}+2\sqrt{21}=21\)

Answer 2

giải giúp em bài 6 ạ

 

Answer 3

6. a) -1

    b) 10

    c) 6

    d) 21