a: \(\sqrt{252}+\dfrac{1}{3}\sqrt{63}-\sqrt{175}\)

\(=4\sqrt{7}+\sqrt{7}-5\sqrt{7}\)

=0

a:

-2/5 + 4/5.x = 3/5

2/5 . x = 3/5

x = 3/5 : 2/5

x = 15/10

\(a,\dfrac{-2}{5}+\dfrac{4}{5}x=\dfrac{3}{5}\)

\(\Rightarrow\dfrac{4x-2}{5}=\dfrac{3}{5}\)

\(\Rightarrow4x-2=3\)

\(\Rightarrow4x=5\)

\(\Rightarrow x=\dfrac{5}{4}\)

\(b,\dfrac{-3}{7}-\dfrac{4}{7}:x=-2\)

\(\Rightarrow\dfrac{-4}{7x}=\dfrac{-11}{7}\)

\(\Rightarrow7x=\dfrac{-4.7}{-11}\)

\(\Rightarrow7x=\dfrac{28}{11}\)

\(\Rightarrow x=\dfrac{4}{11}\)

\(\dfrac{a}{b}=-\dfrac{4}{9}\)

BÀI 3:

bài 4:

Là mấy bài này em làm được bài nào chưa?

em ơi, đề khó đọc quá

khó đọc quá bn ơi mik ko cs đọc đc á

nhìn khó đọc quá

\(\Leftrightarrow4x^2-12x-4x^2+9=-3\)

=>-12x=-12

hay x=1

\(4x\left(x-3\right)-\left(2x+3\right)\left(2x-3\right)=-3\)

\(4x^2-12x-4x^2+9+3=0\)

\(12-12x=0\\ \Rightarrow1-x=0\\ \Rightarrow x=1\)

mik hok bt bn tra gg đi

...??? 

b) \(=\left(5+2\sqrt{3}\right).\sqrt{25-2.5.2\sqrt{3}+12}\\ =\left(5+2\sqrt{3}\right).\sqrt{\left(5-2\sqrt{3}\right)^2}=\left(5+2\sqrt{3}\right).\left(5-2\sqrt{3}\right)=25-12=13\)

c: \(\left(2-\dfrac{5-\sqrt{5}}{1-\sqrt{5}}\right)\left(\dfrac{\sqrt{10}+\sqrt{5}}{\sqrt{2}+1}-2\right)\)

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

=1

\(b,=\left(5+2\sqrt{3}\right)\sqrt{\left(5-2\sqrt{3}\right)^2}=\left(5+2\sqrt{3}\right)\left(5-2\sqrt{3}\right)=25-12=13\\ c,=\left(2-\dfrac{\sqrt{5}\left(\sqrt{5}-1\right)}{1-\sqrt{5}}\right)\left(\dfrac{\sqrt{5}\left(\sqrt{2}+1\right)}{\sqrt{2}+1}-2\right)\\ =\left(2+\sqrt{5}\right)\left(\sqrt{5}-2\right)=5-4=1\)