\(\left(x-3\right)\left(x+7\right)-\left(x+5\right)\left(x-1\right)\)

\(=x^2+7x-3x-21-\left(x^2-x+5x-5\right)\)

\(=x^2+4x-21-x^2-4x+5\)

\(=-16\)

Vài cái sai đề

với lại đề kiểu đó ai đọc đc

a) 23,45hm = …… 3,45 = …… b) 2,345hm = …… 34,5dam = …… c) 234,55m = …… 2,3456m = …… d) 1234,5m = …… 345 , 67phút = ……

\(\left(\frac{1}{x+2\sqrt{x}}-\frac{1}{\sqrt{x}+2}\right)\div\frac{1-\sqrt{x}}{x+4\sqrt{x}+4}\)

ĐKXĐ : \(\hept{\begin{cases}x>0\\x\ne1\end{cases}}\)

\(=\left(\frac{1}{\sqrt{x}\left(\sqrt{x}+2\right)}-\frac{1}{\sqrt{x}+2}\right)\div\frac{1-\sqrt{x}}{\left(\sqrt{x}+2\right)^2}\)

\(=\left(\frac{1}{\sqrt{x}\left(\sqrt{x}+2\right)}-\frac{\sqrt{x}}{\sqrt{x}\left(\sqrt{x}+2\right)}\right)\div\frac{1-\sqrt{x}}{\left(\sqrt{x}+2\right)^2}\)

\(=\frac{1-\sqrt{x}}{\sqrt{x}\left(\sqrt{x}+2\right)}\times\frac{\left(\sqrt{x}+2\right)^2}{1-\sqrt{x}}\)

\(=\frac{\sqrt{x}+2}{\sqrt{x}}\)

=> đpcm

đéo biết

\(\frac{1}{2}\left(4x-6\right)-1=2\left(\frac{1}{2}x+3\right)\)

\(\Leftrightarrow2x-3-1=x+6\)

\(\Leftrightarrow2x-4=x+6\)

\(\Leftrightarrow x=10\)

vậy......

Y : 7 = 5

\(\Leftrightarrow\)Y = 35

\(\Leftrightarrow\)Y + 119 + 36 + 17 + 19 = 35 + 119 + 36 + 17 + 19 = 226

y=226

= 100000

đề bài này sai rồi ! 

2354Y5EJYRU5421W3ERTHJY432ER

4 050 154 / 4 050 154

ok bạn nhớ !!!