Câu 1:
a: Ta có: \(\left(\sqrt{28}-2\sqrt{14}+\sqrt{7}\right)\cdot\sqrt{7}+7\sqrt{8}\)
\(=\left(3\sqrt{7}-2\sqrt{14}\right)\cdot\sqrt{7}+14\sqrt{2}\)
\(=21-14\sqrt{2}+14\sqrt{2}\)
=21
b: Ta có: \(\left(\dfrac{1}{3-2\sqrt{2}}-\dfrac{6}{2+\sqrt{2}}\right)\left(5\sqrt{2}+3\right)\)
\(=\left(3+2\sqrt{2}-6+3\sqrt{2}\right)\left(5\sqrt{2}+3\right)\)
\(=\left(5\sqrt{2}-3\right)\left(5\sqrt{2}+3\right)\)
=41
c: Ta có: \(\dfrac{4}{\sqrt{3}+1}-\dfrac{5}{\sqrt{3}-2}+\dfrac{6}{\sqrt{3}-3}\)
\(=-2+2\sqrt{3}+10+5\sqrt{3}-3-\sqrt{3}\)
\(=6\sqrt{3}+5\)
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