giúp mình vs ạ !
a, \(\left(2\sqrt{45}+\sqrt{80}-\sqrt{125}\right).\sqrt{5}\)
\(=\left(2\sqrt{9.5}+\sqrt{16.5}-\sqrt{25.5}\right).\sqrt{5}\)
\(=\left(2.3\sqrt{5}+4\sqrt{5}-5\sqrt{5}\right).\sqrt{5}\)
\(=\left(6\sqrt{5}+4\sqrt{5}-5\sqrt{5}\right).\sqrt{5}\)
\(=30+20-25\)
\(=25\)
b, \(2\sqrt{\dfrac{16}{5}}-3\sqrt{\dfrac{1}{45}}-6\sqrt{\dfrac{4}{20}}\)
\(=2.4\sqrt{\dfrac{1}{5}}-3.\dfrac{1}{3}\sqrt{\dfrac{1}{5}}-6.\dfrac{2}{2}\sqrt{\dfrac{1}{5}}\)
\(=8\sqrt{\dfrac{1}{5}}-\sqrt{\dfrac{1}{5}}-6\sqrt{\dfrac{1}{5}}\)
\(=\sqrt{\dfrac{1}{5}}=\dfrac{\sqrt{5}}{5}\)
c, \(3-\sqrt{7-2\sqrt{6}}-3\sqrt{6}\)
\(=3-\sqrt{6-2\sqrt{6}+1}-3\sqrt{6}\)
\(=3-\sqrt{\left(\sqrt{6}\right)^2-2\sqrt{6}+1^2}-3\sqrt{6}\)
\(=3-\sqrt{\left(\sqrt{6}-1\right)^2}-3\sqrt{6}\)
\(=3-\left|\sqrt{6}-1\right|-3\sqrt{6}\)
\(=3-\left(\sqrt{6}-1\right)-3\sqrt{6}\)
\(=3-\sqrt{6}+1-3\sqrt{6}\)
\(=4-4\sqrt{6}\)
d, \(\dfrac{3}{\sqrt{5}+\sqrt{2}}-\dfrac{4}{3-\sqrt{5}}+\dfrac{1}{\sqrt{2}-1}\)
\(=\dfrac{3\left(\sqrt{5}-\sqrt{2}\right)}{\left(\sqrt{5}+\sqrt{2}\right)\left(\sqrt{5}-\sqrt{2}\right)}-\dfrac{4\left(3+\sqrt{5}\right)}{\left(3-\sqrt{5}\right)\left(3+\sqrt{5}\right)}+\dfrac{\sqrt{2}+1}{\left(\sqrt{2}-1\right)\left(\sqrt{2}+1\right)}\)
\(=\dfrac{3\left(\sqrt{5}-\sqrt{2}\right)}{3}-\dfrac{4\left(3+\sqrt{5}\right)}{4}+\dfrac{\sqrt{2}+1}{1}\)
\(=\sqrt{5}-\sqrt{2}-\left(3+\sqrt{5}\right)+\sqrt{2}+1\)
\(=\sqrt{5}-\sqrt{2}-3-\sqrt{5}+\sqrt{2}+1\)
\(=-2\)
a) Ta có: \(\left(2\sqrt{45}+\sqrt{80}-\sqrt{125}\right)\cdot\sqrt{5}\)
\(=30+20-25\)
=25
Giúp mình vs ạ. Cảm ơn trước ạ!
giúp mình vs ạ,mình cảm ơn
giúp mình vs ạ !
giúp mình vs ạ !