a, \(4\sqrt{18}+2\sqrt{2}-5\sqrt{8}+\sqrt{32}\)
\(=12\sqrt{2}+2\sqrt{2}-5\sqrt{8}+\sqrt{32}\)
\(=12\sqrt{2}+2\sqrt{2}-10\sqrt{2}+\sqrt{32}\)
\(=12\sqrt{2}+2\sqrt{2}-10\sqrt{2}+4\sqrt{2}\)
\(=8\sqrt{2}\)
b,
c, \(\sqrt{150}+\sqrt{240}-3\sqrt{\dfrac{8}{3}}-3\sqrt{6}\)
\(=5\sqrt{6}+4\sqrt{15}-\dfrac{6\sqrt{6}}{3}-3\sqrt{6}\)
\(=0\sqrt{6}+4\sqrt{15}\)
\(=0+4\sqrt{15}\)
\(=4\sqrt{15}\)
2.
a,\(\dfrac{2}{\sqrt{3-1}}-\dfrac{2}{\sqrt{3-1}}=0\)
b,\(\dfrac{5+\sqrt{5}}{5-\sqrt{5}}+\dfrac{5-\sqrt{5}}{5+\sqrt{5}}\)
\(=\dfrac{5+\sqrt{5}}{5-\sqrt{5}}x\dfrac{5+\sqrt{5}}{5+\sqrt{5}}+\dfrac{5-\sqrt{5}}{5+\sqrt{5}}\)
\(=\dfrac{5x5+5\sqrt{5}+\sqrt{5}x5+\sqrt{5}\sqrt{5}}{\left(5-\sqrt{5}\right)\left(5+\sqrt{5}\right)}+\dfrac{5-\sqrt{ }}{5+\sqrt{5}}\)
\(=\dfrac{3+\sqrt{5}}{2}+\dfrac{5-\sqrt{5}}{5+\sqrt{5}}x\dfrac{5-\sqrt{5}}{5-\sqrt{5}}\)
\(=\dfrac{3+5}{2}+\dfrac{5x5+5x\left(-\sqrt{5}\right)-\sqrt{5}x5-\sqrt{5}x\left(-\sqrt{5}\right)}{\left(5+\sqrt{5}\right)\left(5-\sqrt{5}\right)}\)
\(=\dfrac{3+\sqrt{5}}{2}+\dfrac{5x5+5x\left(-\sqrt{5}\right)-\sqrt{5}x5-\sqrt{5}x\left(-\sqrt{5}\right)}{5^5-\left(\sqrt{5}\right)^2}\)
\(=3\)
c,\(\dfrac{x\sqrt{x}-y\sqrt{y}}{\sqrt{x}-\sqrt{y}}=\dfrac{\left(\sqrt{x}\right)^3-\left(\sqrt{y}\right)^3}{\sqrt{x}-\sqrt{y}}\)
\(=\dfrac{\left(\sqrt{x}-\sqrt{y}\right)\left[\left(\sqrt{x}\right)^2+\sqrt{x}.\sqrt{y}+\left(\sqrt{y}\right)^2\right]}{\sqrt{x}-\sqrt{y}}\)
\(=x+\sqrt{xy}+y\)
Bạn ơi các câu trên thì dấu x là dấu nhân chỉ có câu cuối của bài 2 là chữ x á nha :)) với lại câu 2 bài 1 mik ko lm đc nha hihi