Question

Đưa thừa số ra ngoài dấu căn :

a) \(4\sqrt{3\:}\) + \(\sqrt{27}\) - \(\sqrt{45}\) + \(\sqrt{5}\)

b) \(\sqrt{28a^4b^{2\:}}\) với b ≥ 0

c) \(\sqrt{72a^2b^4}\) với a < 0

Answer 1

a) = \(4\sqrt{3}+3\sqrt{3}-3\sqrt{5}+\sqrt{5}=\sqrt{3}\cdot\left(4+3\right)-\sqrt{5}\cdot\left(3-1\right)=7\sqrt{3}-2\sqrt{5}\)

Answer 2

b) = \(2a^2b\sqrt{7b}\)

c) = \(6ab^2\sqrt{2}\)

Answer 3

a. \(4\sqrt{3}+\sqrt{27}-\sqrt{45}+\sqrt{5}=4\sqrt{3}+3\sqrt{3}-3\sqrt{5}+\sqrt{5}=\left(4+3\right)\sqrt{3}-\left(3-1\right)\sqrt{5}=7\sqrt{3}-2\sqrt{5}\)b. \(\sqrt{28a^4b^2}=2a^2b\sqrt{7}\)( vì b>=0)

c.\(\sqrt{72a^2b^4}=-6ab^2\sqrt{2}\)( vì a<o)