cvfbhm,

Xin lỗi em ko biết làm , em vẫn chưa lên lớp 9

1)\(\left(\frac{1}{a-\sqrt{a}}+\frac{1}{\sqrt{a}-1}\right):\frac{\sqrt{a}+1}{a-2\sqrt{a}+1}\)

\(=\left(\frac{1}{\sqrt{a}\left(\sqrt{a}-1\right)}+\frac{\sqrt{a}}{\sqrt{a}\left(\sqrt{a}-1\right)}\right)\cdot\frac{\left(\sqrt{a}-1\right)^2}{\sqrt{a}+1}\)

\(=\frac{\sqrt{a}+1}{\sqrt{a}\left(\sqrt{a}-1\right)}\cdot\frac{\left(\sqrt{a}-1\right)^2}{\sqrt{a}+1}\)

\(=\frac{\sqrt{a}-1}{\sqrt{a}}\)

a) \(\frac{3}{4}+\frac{1}{4}:x=-3\)

\(\frac{1}{4}:x=-3-\frac{3}{4}\)

\(\frac{1}{4}:x=\frac{-15}{4}\)

\(x=\frac{1}{4}:\frac{-15}{4}\)

\(x=\frac{-1}{15}\)

b) \(x-\frac{1}{2}=2,5-x\)

\(x+x=2,5+\frac{1}{2}\)

\(2x=3\)

\(x=\frac{3}{2}\)

c) \(\left(x+\frac{1}{10}\right)+\left(x+\frac{1}{11}\right)=0\)

\(2x+\frac{21}{110}=0\)

\(2x=\frac{-21}{110}\)

\(x=\frac{-21}{110}:2\)

\(x=\frac{-21}{220}\)

Em nên đánh rõ các dấu giùm cho mọi người dễ hiểu !

CÓ AI BIẾT CÂU 5/6 NHÂN X =3/7 KO

CHẳng hỉu j

ĐKXĐ ; \(x\ne\pm1\)

Ta có : \(\dfrac{x+1}{x-1}-\dfrac{x-1}{x+1}+\dfrac{x^2+3}{1-x^2}=0\)

\(\Leftrightarrow\dfrac{\left(x+1\right)^2}{x^2-1}-\dfrac{\left(x-1\right)^2}{x^2-1}+\dfrac{-x^2-3}{x^2-1}=0\)

\(\Leftrightarrow\left(x+1\right)^2-\left(x-1\right)^2-x^2-3=0\)

\(\Leftrightarrow x^2+2x+1-x^2+2x-1-x^2-3=0\)

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

\(\Leftrightarrow-x^2+3x+x-3=0\)

\(\Leftrightarrow-x\left(x-3\right)+\left(x-3\right)=0\)

\(\Leftrightarrow\left(x-3\right)\left(x-1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=3\left(TM\right)\\x=1\left(L\right)\end{matrix}\right.\)

=> X = 3

Vậy ..