Question

Giúp mình bài 6B với ạk

Answer 1

a) \(\dfrac{\sqrt{28y^6}}{\sqrt{7y^4}}=\sqrt{\dfrac{28y^6}{7y^4}}=\sqrt{4y^2}=\left|2y\right|=-2y\left(y< 0\right)\)

b) \(\sqrt{\dfrac{14a}{b}}.\sqrt{\dfrac{7ab^3}{2}}=\sqrt{\dfrac{14a}{b}.\dfrac{7ab^3}{2}}=\sqrt{49a^2b^2}=\left|7ab\right|\)

\(==7\left(-a\right)\left(-b\right)\left(a,b< 0\right)=7ab\)

c) \(\sqrt{\sqrt{x^4+4}-x^2}.\sqrt{\sqrt{x^4+4}+x^2}\)

\(=\sqrt{\left(\sqrt{x^4+4}-x^2\right)\left(\sqrt{x^4+4}+x^2\right)}\)

\(=\sqrt{x^4+4-\left(x^2\right)^2}=\sqrt{4}=2\)