Question

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Answer 1

Tick nha
1)
\(A=\dfrac{2}{2-\sqrt{3}}-\sqrt{12}+\dfrac{\sqrt{18}}{\sqrt{2}}\)
\(A=\dfrac{2\left(2+\sqrt{3}\right)}{\left(2-\sqrt{3}\right)\left(2+\sqrt{3}\right)}-\sqrt{12}+\dfrac{\sqrt{18}.\sqrt{2}}{\sqrt{2}.\sqrt{2}}\)
\(A=\dfrac{2\left(2+\sqrt{3}\right)}{4-3}-\sqrt{12}+\dfrac{6}{2}\)
\(A=2\left(2+\sqrt{3}\right)-\sqrt{12}+3\)
\(A=4+2\sqrt{3}-2\sqrt{3}+3\)
\(A=7\)
2)
\(A=2\sqrt{8}-5\sqrt{18}+4\sqrt{32}\)
\(A=2.2\sqrt{2}-5.3\sqrt{2}+4.4\sqrt{2}\)
\(A=4\sqrt{2}-15\sqrt{2}+16\sqrt{2}\)
\(A=5\sqrt{2}\)
 

Answer 2

Tick
\(B=\dfrac{a-\sqrt{a}}{a-2\sqrt{a}+1}.\left(1-\sqrt{a}\right)\) với a>1
\(B=\dfrac{\sqrt{a}\left(\sqrt{a}-1\right)}{\left(\sqrt{a}-1\right)^2}\left(1-\sqrt{a}\right)\)
\(B=\dfrac{\sqrt{a}}{\sqrt{a}-1}\left(1-\sqrt{a}\right)\)
\(B=\dfrac{-\sqrt{a}}{1-\sqrt{a}}\left(1-\sqrt{a}\right)\)
\(B=-\sqrt{a}\)

Answer 3

4)
\(A=\sqrt{20}-\sqrt{45}+\sqrt{6+2\sqrt{5}}\)
\(A=2\sqrt{5}-3\sqrt{5}+\sqrt{5+2\sqrt{5}+1}\)
\(A=-\sqrt{5}+\sqrt{\left(\sqrt{5}+1\right)^2}\)
\(A=-\sqrt{5}+\sqrt{5}+1\)
A=1

Answer 4

4: Ta có: \(A=\sqrt{20}-\sqrt{45}+\sqrt{6+2\sqrt{5}}\)

\(=2\sqrt{5}-3\sqrt{5}+\sqrt{5}+1\)

=1