chắc là ......giờ tớ nhớ được tớ để sách lớp 8 ở đâu -.- ... thôi thì cứ làm đại.
a) \(\dfrac{1}{x-1}+3=x-\dfrac{3}{2-x}\)
đk: x khác 1, x khác 2
pt đã cho \(\Leftrightarrow2-x-3x^2+9x-6-x^2+4x-3=0\)
\(\Leftrightarrow4x^2-12x+7=0\Leftrightarrow4\left(x-\dfrac{-3+\sqrt{2}}{2}\right)\left(x-\dfrac{-3-\sqrt{2}}{2}\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-3-\sqrt{2}}{2}\left(N\right)\\x=\dfrac{-3+\sqrt{2}}{x}\left(N\right)\end{matrix}\right.\)
Kl: \(x=\dfrac{-3-\sqrt{2}}{2}\), \(x=\dfrac{-3+\sqrt{2}}{2}\)
từng câu cho nhanh nhé, sorry, nãy giờ mải làm việc riêng nên trả lời bạn hơi lâu
b) \(\dfrac{2x-2x^2}{x+3}+\dfrac{4x}{x+3}=\dfrac{2}{7}\)
Đk: x khác -3
pt đã cho \(\Leftrightarrow\dfrac{6x-2x^2}{x+3}=\dfrac{2}{7}\Leftrightarrow\dfrac{2x\left(3-x\right)}{x+3}=\dfrac{2}{7}\)
\(\Leftrightarrow\dfrac{x\left(3-x\right)}{x+3}-\dfrac{x+3}{7\left(x+3\right)}=0\)
\(\Leftrightarrow\dfrac{1}{x+3}\left(20x-7x^2-3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{10+\sqrt{79}}{7}\left(N\right)\\x=\dfrac{10-\sqrt{79}}{7}\left(N\right)\end{matrix}\right.\)
Kl: ..............
c) \(\dfrac{x+1}{x-1}-\dfrac{x-1}{x+1}=\dfrac{4}{x^2-1}\)
Đk: x khác +-1
pt đã cho \(\Leftrightarrow\dfrac{4x}{x^2-1}=\dfrac{4}{x^2-1}\Leftrightarrow x=1\left(L\right)\)
Kl: ptvn
d) \(\dfrac{3x-2}{x+7}=\dfrac{6x+1}{2x-3}\)
Đk: \(\left\{{}\begin{matrix}x\ne-7\\x\ne\dfrac{3}{2}\end{matrix}\right.\)
pt đã cho \(\Leftrightarrow\dfrac{3x-2}{x+7}=\dfrac{6x+1}{2x-3}\Leftrightarrow\dfrac{6x^2-13x+6}{\left(x+7\right)\left(2x-3\right)}=\dfrac{6x^2+43x+7}{\left(x+7\right)\left(2x-3\right)}\Leftrightarrow\dfrac{1}{\left(x+7\right)\left(2x-3\right)}\left(-56x-1\right)=0\)
\(\Leftrightarrow x=-\dfrac{1}{56}\left(N\right)\)
KL: x=-1/56
