\(\dfrac{18}{30}=\dfrac{18:6}{30:6}=\dfrac{3}{5}\)

`6*x-5=19`

`6*x=19+5`

`6*x=24`

`x=24/6`

`x=4`

Vậy `x=4`

Bài `2`

`a,4x+6y`

`= 2(2x+3y)`

`b, 3x^2-6xy +3y^2`

`= 3(x^2 -2xy +y^2)`

`=3(x-y)^2`

`c, x^2+2x -y^2+2y`

`= (x^2-y^2)+(2x+2y)`

`=(x-y)(x+y) +2(x+y)`

`=(x+y)(x-y+2)`

có fb là có cả đống mặt liền ⚡

\(\sqrt{x^2-9}-3\sqrt{x-3}=0\\ \Leftrightarrow\sqrt{\left(x-3\right)\left(x+3\right)}-3\sqrt{x-3}=0\\ \Leftrightarrow\sqrt{x-3}\cdot\sqrt{x+3}-3\sqrt{x-3}=0\\ \Leftrightarrow\left(\sqrt{x-3}\right)\left(\sqrt{x+3}-3\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}\sqrt{x-3}=0\\\sqrt{x+3}-3=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}\sqrt{x-3}=0\\\sqrt{x+3}=3\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x-3=0\\x+3=9\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=3\\x=6\end{matrix}\right.\)

\(\dfrac{1}{3}\sqrt{72}-3\sqrt{50}-\dfrac{\sqrt{66}}{\sqrt{33}}\\ =\dfrac{1}{3}\sqrt{36\cdot2}-3\sqrt{25\cdot2}-\sqrt{\dfrac{66}{33}}\\ =\dfrac{1}{3}\cdot6\sqrt{2}-3\cdot5\sqrt{2}-\sqrt{2}\\ =2\sqrt{2}-15\sqrt{2}-\sqrt{2}\\ =-14\sqrt{2}\)

\(b,2\sqrt{3x}-\sqrt{75x}+\dfrac{1}{2}\sqrt{48x}\\ =2\sqrt{3x}-\sqrt{25\cdot3x}+\dfrac{1}{2}\sqrt{16\cdot3}\\ =2\sqrt{3x}-5\sqrt{3x}+\dfrac{1}{2}\cdot4\sqrt{3x}\\ =2\sqrt{3x}-5\sqrt{3x}+2\sqrt{3x}\\ =-\sqrt{3x}\)

keke=)))

bảo dễ nuôi mà thế=))