\(\frac{1}{x^2-3x+2}-\frac{1}{x-2}=2\)
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11 tháng 12 2019
\(a)=\frac{-2\left(x+3\right)}{x\left(1-3x\right)}.\frac{1-3x}{x\left(x+3\right)}\)
\(=\frac{-2}{x^2}\)
\(b)=\frac{\left(x+3\right)\left(x-3\right)}{x\left(x-3\right)}-\frac{x^2}{x\left(x-3\right)}+\frac{9}{x\left(x-3\right)}\)
\(=\frac{x^2-3x+3x-9-x^2+9}{x\left(x-3\right)}\)
\(=x\left(x-3\right)\)
\(c)=\frac{x+3}{\left(x-1\right)\left(x+1\right)}-\frac{1}{x\left(x+1\right)}\)
\(=\frac{\left(x+3\right).x}{x\left(x-1\right)\left(x+1\right)}-\frac{1.\left(x-1\right)}{x\left(x-1\right)\left(x+1\right)}\)
\(=\frac{x^2+3x-x+1}{x\left(x-1\right)\left(x+1\right)}\)
\(=\frac{x\left(x+3\right)-\left(x-1\right)}{x\left(x-1\right)\left(x+1\right)}\)
\(=\frac{x+3}{x+1}\)
# Sắp ik ngủ nên làm vậy hoi, ko chắc phần kq câu b và c đâu nha
N
31 tháng 12 2018
a) \(=\frac{3x+2}{\left(3x+2\right).\left(3x-2\right)}-\frac{12x-8}{\left(3x+2\right).\left(3x-2\right)}-\frac{-3x+6}{\left(3x-2\right).\left(3x+2\right)}\)
\(b,\frac{x^2+1}{\left(x-1\right).\left(x^2+1\right)}-\frac{x.\left(x^2-1\right).\left(x-1\right)}{\left(x-1\right).\left(x^2+1\right)}.\left(\frac{1}{\left(x-1\right)^2}-\frac{1}{\left(x+1\right).\left(x-1\right)}\right)\)
p/s: hướng dấn cách tách thoy, tự làm nha~~lazy
31 tháng 12 2018
a )
\(\frac{1}{3x-2}-\frac{4}{3x+2}-\frac{3x-6}{4-9x^2}=0\)
\(\Leftrightarrow\frac{\left(3x+2\right)-4.\left(3x-2\right)}{9x^2-4}=\frac{3x-6}{4-9x^2}\) ( * )
Đkxđ : \(\hept{\begin{cases}9x^2-4\ne0\\4-9x^2\ne0\end{cases}}\Leftrightarrow\hept{\begin{cases}x\ne\pm\sqrt{\frac{4}{9}}\\x\ne\pm\sqrt{\frac{4}{9}}\end{cases}}\Leftrightarrow x\ne\pm\frac{2}{3}\)
( * ) => \(\left(4-9x^2\right).\left[\left(3x+2\right)+\left(-12x+8\right)\right]=\left(9x^2-4\right).\left(3x-6\right)\)
\(\Leftrightarrow\left(4-9x^2\right).\left(-9x+10\right)=\left(9x^2-4\right).\left(3x-6\right)\)
\(\Leftrightarrow-36x+40+81x^3-90x^2=27x^3-54x^2-12x+24\)
\(\Leftrightarrow54x^3-36x^2-24x+16=0\)
\(\Leftrightarrow\orbr{\begin{cases}x=\frac{2}{3}\left(loai\right)\\x=-\frac{2}{3}\left(loai\right)\end{cases}}\)
Vậy : phương trình vô nghiệm
KN
20 tháng 11 2019
a) \(\frac{3x^2-6xy+3y^2}{5x^2-5xy+5y^2}:\frac{10x-10y}{x^3+y^3}\)
\(=\frac{3x^2-6xy+3y^2}{5x^2-5xy+5y^2}.\frac{x^3+y^3}{10x-10y}\)
\(=\frac{3\left(x^2-2xy+y^2\right)}{5\left(x^2-xy+y^2\right)}.\frac{\left(x+y\right)\left(x^2-xy+y^2\right)}{10\left(x-y\right)}\)
\(=\frac{3\left(x^2-2xy+y^2\right)}{5}.\frac{x+y}{10\left(x-y\right)}\)
\(=\frac{3\left(x-y\right)^2}{5}.\frac{x+y}{10\left(x-y\right)}\)
\(=\frac{3\left(x-y\right)}{5}.\frac{x+y}{10}\)
\(=\frac{3x^2-3y^2}{50}\)
KN
20 tháng 11 2019
c) \(\frac{2}{xy}:\left(\frac{1}{x}-\frac{1}{y}\right)-\frac{x^2-y^2}{\left(x-y\right)^2}\)
\(=\frac{2}{xy}:\frac{y-x}{xy}-\frac{\left(x+y\right)\left(x-y\right)}{\left(x-y\right)^2}\)
\(=\frac{2}{y-x}-\frac{x+y}{x-y}\)
\(=\frac{2}{y-x}+\frac{x+y}{y-x}\)
\(=\frac{x+y+2}{y-x}\)
\(\frac{1}{x^2-3x+2}-\frac{1}{x-2}=2\) đkxđ \(x\ne1;2\)
\(\Leftrightarrow\frac{1}{\left(x-1\right)\left(x-2\right)}-\frac{1}{x-2}=2\)
\(\Leftrightarrow\frac{1}{\left(x-1\right)\left(x-2\right)}-\frac{1\left(x-1\right)}{\left(x-2\right)\left(x-1\right)}=2\)
\(\Leftrightarrow1-x+1=2\)
\(\Leftrightarrow2-x=2\)
\(\Leftrightarrow x=0\left(tmđk\right)\)