Question

Answer 1

Bài 6: 

a) Ta có: \(2\sqrt{a^2}-3a\)

\(=-2a-3a\)

=-5a

b) Ta có: \(5\sqrt{4a^6}+4a^3\)

\(=5\cdot2\cdot\left(-a^3\right)+4a^3\)

\(=-10a^3+4a^3\)

\(=-6a^3\)

Answer 2

Bài 7:

a) Ta có: \(\sqrt{9-4\sqrt{5}}-\sqrt{5}\)

\(=\sqrt{5}-2-\sqrt{5}\)

=-2

b) Ta có: \(\sqrt{8+2\sqrt{15}}-\sqrt{3}+2\sqrt{5}\)

\(=\sqrt{5}+\sqrt{3}-\sqrt{3}+2\sqrt{5}\)

\(=3\sqrt{5}\)

Answer 3

Bài 5: 

a) ĐKXĐ: \(x\ge-\dfrac{5}{2}\)

b) ĐKXĐ: \(x\le\dfrac{3}{4}\)

c) ĐKXĐ: x<-3

d) ĐKXĐ: \(x\ge3\)