Question

[nguyễn thái hồng duyên]

1. làm tính nhân :

a)\(\left(\sqrt{12}-3\sqrt{75}\right).\sqrt{3}\)

b) \(\left(\sqrt{18}-4\sqrt{72}\right).2\sqrt{2}\)

c) \(\left(\sqrt{6}-2\right)\left(\sqrt{6}+7\right)\)

d) \(\left(\sqrt{3}+2\right)\left(\sqrt{3}-5\right)\)

2) thực hien phep tinh :

a) \(\left(\sqrt{48}-\sqrt{27}+4\sqrt{12}\right):\sqrt{3}\)

b) \(\left(\sqrt{20}-3\sqrt{45}+6\sqrt{180}\right):\sqrt{5}\)

c) \(\left(2\sqrt{20}-3\sqrt{45}+4\sqrt{80}\right):\sqrt{5}\)

d) \(\left(3\sqrt{24}+4\sqrt{54}-5\sqrt{96}\right):\sqrt{6}\)

e)\(\left(\sqrt{x^2y}-\sqrt{xy^2}\right):\sqrt{xy}\)

f) \(\left(\sqrt{a^3b}+\sqrt{ab^3}-ab\right):\sqrt{ab}\)

g) \(\left(3\sqrt{x^2y}-4\sqrt{xy^2}+5xy\right):\sqrt{xy}\)

h) \(\left(\sqrt{a^3b}+\sqrt{ab^3-3\sqrt{ab}}\right):\sqrt{ab}\)

Answer 1

[Trần Thị Băng Tâm]

1.a) (\(\sqrt{12}\) -3\(\sqrt{75}\))\(\sqrt{3}\)

=\(\sqrt{12}\).\(\sqrt{3}\)-3\(\sqrt{75}\).\(\sqrt{3}\)

=\(2\sqrt{3}.\sqrt{3}-3.5\sqrt{3}.\sqrt{3}\)

=2.3-15.3

=6-45

= -39

b)\(\left(\sqrt{18}-4\sqrt{72}\right)2\sqrt{2}\)

\(\left(3\sqrt{2}-4.6\sqrt{2}\right).2\sqrt{2}\)

\(\left(3\sqrt{2}-24\sqrt{2}\right).2\sqrt{2}\)

\(3\sqrt{2}.2\sqrt{2}-24\sqrt{2}.2\sqrt{2}\)

= 6.2-48.2 = 12-96= -84

d)\(\left(\sqrt{3}+2\right)\left(\sqrt{3}-5\right)\)

\(3-5\sqrt{3}+2\sqrt{3}-10\)

\(-7-3\sqrt{3}\)

Answer 2

[Nguyễn Huế]

\(\)c)\(\left(\sqrt{6}-2\right)\left(\sqrt{6}+7\right)\)

\(\Leftrightarrow6+6\sqrt{7}-2\sqrt{6}-14\)

\(\Leftrightarrow-8+5\sqrt{6}\)

d)\(\left(\sqrt{3}+2\right)\left(\sqrt{3}-5\right)\)

\(\Leftrightarrow3-5\sqrt{3}+2\sqrt{3}-3\)

\(\Leftrightarrow-3\sqrt{3}\)