cho biểu thức C=\(\left(x^2+\frac{4x^2}{x^2-4}\right).\left(\frac{x}{2x-4}+\frac{2-2x}{x^3-4x}.\frac{x^2-4}{x-2}\right)\)
ai nhanh mink tick cho
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JS
25 tháng 3 2020
1.\(A=\frac{2x^2-16x+41}{x^2-8x+22}\) \(=\frac{2\left(x^2-8x+22\right)-3}{x^2-8x+22}=2-\frac{3}{\left(x-4\right)^2+6}\ge\frac{1}{2}\)
Dấu '' = '' xảy ra khi x = 4.
Vậy MinA= \(\frac{1}{2}\) tại x = 4.
KN
3 tháng 10 2020
\(ĐK:x\ne\pm1;x\ne0;x\ne3\)
Với \(x\ne\pm1;x\ne0;x\ne3\)thì\(M=\frac{x^3+2x^2-x-2}{x^3-2x^2-3x}\left[\frac{\left(x+2\right)^2-x^2}{4x^2-4}-\frac{3}{x^2-x}\right]=\frac{x^2\left(x+2\right)-\left(x+2\right)}{\left(x^3-x\right)-\left(2x^2+2x\right)}\left[\frac{x^2+4x+4-x^2}{4x^2-4}-\frac{3}{x\left(x-1\right)}\right]\)\(=\frac{\left(x-1\right)\left(x+1\right)\left(x+2\right)}{x\left(x+1\right)\left(x-1\right)-2x\left(x+1\right)}\left[\frac{4\left(x+1\right)}{4\left(x+1\right)\left(x-1\right)}-\frac{3}{x\left(x-1\right)}\right]=\frac{\left(x-1\right)\left(x+1\right)\left(x+2\right)}{\left(x+1\right)\left(x^2-3x\right)}\left[\frac{1}{x-1}-\frac{3}{x\left(x-1\right)}\right]\)\(=\frac{\left(x-1\right)\left(x+2\right)}{x\left(x-3\right)}.\frac{x-3}{x\left(x-1\right)}=\frac{x+2}{x^2}\)
M = 3 \(\Leftrightarrow\frac{x+2}{x^2}=3\Leftrightarrow3x^2-x-2=0\Leftrightarrow\left(x-1\right)\left(3x+2\right)=0\Leftrightarrow\orbr{\begin{cases}x=1\\x=\frac{-2}{3}\end{cases}}\)
Mà \(x\ne1\)(theo điều kiện) nên x =-2/3
14 tháng 3 2020
Ta có: \(P=\frac{\left(\frac{2+x}{2-x}+\frac{4x^2}{x^2-4}-\frac{2-x}{2+x}\right)}{\frac{x^2-3x}{2x^2-x^3}}\)
\(=\left(\frac{\left(2+x\right)\left(2+x\right)}{\left(2-x\right)\left(2+x\right)}-\frac{4x^2}{\left(2-x\right)\left(2+x\right)}-\frac{\left(2-x\right)\left(2-x\right)}{\left(2+x\right)\left(2-x\right)}\right)\cdot\frac{x\left(x-3\right)}{x^2\left(2-x\right)}\)
\(=\frac{4+4x+x^2-4x^2-\left(4-4x+x^2\right)}{\left(2-x\right)\left(2+x\right)}\cdot\frac{x-3}{x\left(2-x\right)}\)
\(=\frac{4+4x+x^2-4x^2-4+4x-x^2}{\left(2-x\right)\left(2+x\right)}\cdot\frac{x-3}{x\left(2-x\right)}\)
\(=\frac{-4x^2+8x}{\left(2-x\right)\left(2+x\right)}\cdot\frac{x-3}{x\left(2-x\right)}\)
\(=\frac{4x\left(2-x\right)\cdot\left(x-3\right)}{\left(2-x\right)\left(2+x\right)\cdot x\cdot\left(2-x\right)}=\frac{4\left(x-3\right)}{\left(2-x\right)\left(2+x\right)}=\frac{4x-12}{4-x^2}\)
25 tháng 12 2020
a, \(A=\left(\frac{4}{2x+1}+\frac{4x-3}{\left(x^2+1\right)\left(2x+1\right)}\right)\frac{x^2+1}{x^2+2}\)
\(=\left(\frac{4\left(x^2+1\right)}{\left(2x+1\right)\left(x^2+1\right)}+\frac{4x-3}{\left(x^2+1\right)\left(2x+1\right)}\right)\frac{x^2+1}{x^2+2}\)
\(=\left(\frac{4x^2+4+4x-3}{\left(x^2+1\right)\left(2x+1\right)}\right)\frac{x^2+1}{x^2+2}\)
\(=\frac{\left(2x+1\right)^2}{\left(x^2+1\right)\left(2x+1\right)}\frac{x^2+1}{x^2+2}=\frac{2x+1}{x^2+2}\)
\(C=\left[\frac{x^2.\left(x^2-4\right)+4x^2}{x^2-4}\right].\left[\frac{x}{2.\left(x-2\right)}+\frac{2-2x}{x.\left(x^2-4\right)}.\frac{x^2-4}{x-2}\right]\)
\(C=\frac{x^4-4x^2+4x^2}{x^2-4}.\left[\frac{x}{2.\left(x-2\right)}+\frac{2-2x}{x\left(x-2\right)}\right]\)
\(C=\frac{x^4}{x^2-4}.\left[\frac{x^2}{2x.\left(x-2\right)}+\frac{\left(2-2x\right).2}{2x.\left(x-2\right)}\right]\)
\(C=\frac{x^4}{x^2-4}.\left[\frac{x^2+4-4x}{2x.\left(x-2\right)}\right]\)
\(C=\frac{x^4}{x^2-4}.\frac{\left(x-2\right)^2}{2x.\left(x-2\right)}\)
\(C=\frac{x^4}{\left(x-2\right).\left(x+2\right)}.\frac{\left(x-2\right).\left(x-2\right)}{2x.\left(x-2\right)}\)
\(C=\frac{x^3}{\left(x+2\right).2}\)
Bạn chưa rút gọn hết, Despacito.