`4x^2-4x`

`= 4x(x-1)`

__

`x^2 -2xy +y^2-4`

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

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

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

`2 3/5+1 2/5 xx 3 1/2`

`= (2xx5+3)/5 + (1xx5+2)/5 xx (3xx2+1)/2`

`= 13/5 + 7/5 xx 7/2`

`= 13/5 + 49/10`

`= 26/10 +49/10`

`= 75/10`

`=15/2`

\(\dfrac{a-\sqrt{a}}{1-\sqrt{a}}\\ =\dfrac{\sqrt{a}\left(\sqrt{a}-1\right)}{1-\sqrt{a}}\\ =\dfrac{-\sqrt{a}\left(1-\sqrt{a}\right)}{1-\sqrt{a}}\\ =-\sqrt{a}\\ \dfrac{2+\sqrt{3}}{2-\sqrt{7}}\\ =\dfrac{\left(2+\sqrt{3}\right)\left(2+\sqrt{7}\right)}{4-7}\\ =\dfrac{4+2\sqrt{7}+2\sqrt{3}+\sqrt{21}}{-3}\\\)

\(3xy\sqrt{\dfrac{2}{xy}}\\ =\sqrt{\dfrac{\left(3xy\right)^2\cdot2}{xy}}\\ =\sqrt{\dfrac{9x^2y^2\cdot2}{xy}}\\ =\sqrt{9xy\cdot2}\\ =\sqrt{18xy}\)

\(\dfrac{4}{\sqrt{3}+1}-\dfrac{5}{\sqrt{3}-2}+\dfrac{6}{\sqrt{3}-3}\\ =\dfrac{4\left(\sqrt{3}+1\right)}{3-1}-\dfrac{5\left(\sqrt{3}+2\right)}{3-4}+\dfrac{6\left(\sqrt{3}+3\right)}{3-9}\\ =\dfrac{4\left(\sqrt{3}+1\right)}{2}-\dfrac{5\left(\sqrt{3}+2\right)}{-1}+\dfrac{6\left(\sqrt{3}+3\right)}{-6}\\ =2\sqrt{3}+2+5\sqrt{3}+10-\sqrt{3}-3\\ =6\sqrt{3}+9\)

\(\dfrac{1}{1+\sqrt{5}}+\dfrac{1}{\sqrt{5}+\sqrt{9}}+\dfrac{1}{\sqrt{9}+\sqrt{13}}\\ =\dfrac{1-\sqrt{5}}{1-5}+\dfrac{\sqrt{5}-\sqrt{9}}{5-9}+\dfrac{\sqrt{9}-\sqrt{13}}{9-13}\\ =\dfrac{1-\sqrt{5}+\sqrt{5}-\sqrt{9}+\sqrt{9}-\sqrt{13}}{-4}\\ =\dfrac{1-\sqrt{13}}{-4}\)

`# gvy`

Quen j tầm này trl kiếm tiền nuôi cj ☕

ý là ngta có thể ngắm hết=))) vẻ đẹp tuyệt sắc giai nhân⚡

`(2x+1)^2 =25/4`

`=> (2x+1)^2 =(+- 5/2)^2`

\(\Rightarrow\left[{}\begin{matrix}2x+1=\dfrac{5}{2}\\2x+1=-\dfrac{5}{2}\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}2x=\dfrac{3}{2}\\2x=-\dfrac{7}{2}\end{matrix}\right.\\\Rightarrow\left[{}\begin{matrix}x=\dfrac{3}{4}\\x=-\dfrac{7}{4}\end{matrix}\right.\)

`a, 2,5 km^2 =2,5 xx 1000000=2500000m^2`

`b, 10,4 ha =10,4xx10000=104000m^2`

`c, 0,03 ha=0,03 xx 100=3m^2`

`d, 800dm^2 = 800:100=8m^2`

`e, 80dm^2=80:100=0,8 m^2`

`g, 917dm^2 =917:100=9,17m^2`

(x-y+2) chứ ạ