\(\dfrac{1}{x+3}+\dfrac{8}{\left(x+1\right)\left(x-3\right)}=\dfrac{2x}{x^2-2x-3}\) giải pt
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{-5}{18}+\dfrac{7}{12}-\dfrac{8}{9}=\dfrac{-10}{36}+\dfrac{21}{36}-\dfrac{32}{36}=\dfrac{-7}{12}\)
\(\dfrac{-5}{6}+\dfrac{3}{8}-\dfrac{7}{12}=\dfrac{-20}{24}+\dfrac{9}{24}-\dfrac{14}{24}=\dfrac{-25}{24}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{2x+1}{2x-1}-\dfrac{2x-1}{2x+1}=-\dfrac{6}{1-4x^2}\left(ĐKXĐ:x\ne\pm\dfrac{1}{2}\right)\)
\(\Leftrightarrow\left(2x+1\right)^2-\left(2x-1\right)^2=6\)
\(\Leftrightarrow4x^2+4x+1-\left(4x^2-4x+1\right)=6\)
\(\Leftrightarrow4x^2+4x+1-4x^2+4x-1=6\)
\(\Leftrightarrow8x=6\)
\(\Leftrightarrow x=\dfrac{6}{8}=\dfrac{3}{4}\)
Vậy \(S=\left\{\dfrac{3}{4}\right\}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(1-\left(\dfrac{1}{3}+\dfrac{1}{2}\right)=1-\dfrac{5}{6}=\dfrac{1}{6}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Đáy bé là : 153,75 x 2 : 20,5 = 15 (m)
Đáy lớn : 15 x 2 = 30 (m)
Diện tích : ( 15 + 30) x 20,5 : 2 = 461,25 (m2)
Đáp số:
\(\dfrac{1}{x+3}+\dfrac{8}{\left(x+1\right)\left(x-3\right)}=\dfrac{2x}{x^2-2x-3}\)
* x2 - 2x - 3 = x2- 3x + x - 3 = x(x-3 ) + ( x - 3) = ( x - 3 ) ( x + 1 )
\(\Leftrightarrow\dfrac{1}{x+3}+\dfrac{8}{\left(x+1\right)\left(x-3\right)}=\dfrac{2x}{\left(x-3\right)\left(x+1\right)}\left(ĐKXĐ:x\ne\pm3;x\ne-1\right)\)
\(\Leftrightarrow\left(x+1\right)\left(x-3\right)+8\left(x+3\right)=2x\left(x+3\right)\)
\(\Leftrightarrow x^2-2x+1+8x+24=2x^2+6x\)
\(\Leftrightarrow-x^2+25=0\)
\(\Leftrightarrow x^2-25=0\Leftrightarrow\left(x-5\right)\left(x+5\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=5\\x=-5\end{matrix}\right.\)
Vậy \(S=\left\{-5;5\right\}\)