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\(\frac{1}{a+b-x}=\frac{1}{a}+\frac{1}{b}-\frac{1}{x}\) (ĐKXĐ: x \(\ne\) 0 và x \(\ne\) a + b)
<=> \(\frac{1}{a+b-x}+\frac{1}{x}-\frac{1}{a}-\frac{1}{b}=0\)
<=> \(\frac{x}{x\left(a+b-x\right)}+\frac{a+b-x}{x\left(a+b-x\right)}-\frac{b}{ab}-\frac{a}{ab}\)
<=> \(\frac{a+b}{x\left(a+b-x\right)}-\frac{a+b}{ab}=0\)
<=> \(\left(a+b\right)\left(\frac{1}{x\left(a+b-x\right)}-\frac{1}{ab}\right)=0\)
* Nếu a = - b thì tập nghiệm cuả pt là S = R
* Nếu a \(\ne\) b thì \(\frac{1}{x\left(a+b-x\right)}-\frac{1}{ab}=0\)
<=> \(\frac{ab}{abx\left(a+b-x\right)}-\frac{x\left(a+b-x\right)}{abx\left(a+b-x\right)}=0\)
<=> \(\frac{ab-\text{ax}-bx+x^2}{abx\left(a+b-x\right)}=0\)
<=> \(\frac{b\left(a-x\right)-x\left(a-x\right)}{abx\left(a+b-x\right)}=0\)
<=> \(\frac{\left(a-x\right)\left(b-x\right)}{abx\left(a+b-x\right)}=0\)
<=> \(\left[\begin{matrix}a-x=0\\b-x=0\end{matrix}\right.\)
<=> \(\left[\begin{matrix}x=a\\x=b\end{matrix}\right.\)
Vậy tập nghiệm của pt là S = {a ; b}
\(\frac{x+1}{x^2+x+1}-\frac{x-1}{x^2-x+1}=\frac{3}{x\left(x^4+x^2+1\right)}\) (ĐKXĐ: x \(\ne\) 0
<=> \(\frac{x\left(x+1\right)\left(x^2-x+1\right)}{x\left(x^2+x+1\right)\left(x^2-x+1\right)}-\frac{x\left(x-1\right)\left(x^2+x+1\right)}{x\left(x^2-x+1\right)\left(x^2+x+1\right)}=\frac{3}{x\left(x^2+x+1\right)\left(x^2-x+1\right)}\)
=> \(\left(x^4+x\right)-\left(x^4-x\right)=3\)
<=> \(2x-3=0\)
<=> \(x=\frac{3}{2}\) (nhận)
Vậy S = {1,5}
a) Qui đồng rồi khử mẫu ta được:
3(3x+2)-(3x+1)=2x.6+5.2
<=> 9x+6-3x-1 = 12x+10
<=> 9x-3x-12x = 10-6+1
<=> -6x = 5
<=> x = -5/6
Vậy ....
b) ĐKXĐ: \(x\ne\pm2\)
Qui đồng rồi khử mẫu ta được:
(x+1)(x+2)+(x-1)(x-2) = 2(x2+2)
<=> x2+3x+2+x2-3x+2 = 2x2+4
<=> x2+x2-2x2+3x-3x = 4-2-2
<=> 0x = 0
<=> x vô số nghiệm
Vậy x vô số nghiệm với x khác 2 và x khác -2
c) \(\left(2x+3\right)\left(\frac{3x+7}{2-7x}+1\right)=\left(x-5\right)\left(\frac{3x+8}{2-7x}+1\right)\) (ĐKXĐ:x khắc 2/7)
\(\Leftrightarrow\left(2x+3\right)\left(\frac{3x+8}{2-7x}+1\right)-\left(x-5\right)\left(\frac{3x+8}{2-7x}+1\right)=0\)
\(\Leftrightarrow\left(\frac{3x+8}{2-7x}+1\right)\left[\left(2x+3\right)-\left(x-5\right)\right]=0\)
\(\Leftrightarrow\left(\frac{3x+8}{2-7x}+1\right)\left(x+8\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}\frac{3x+8}{2-7x}+1=0\\x+8=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}\frac{3x+8}{2-7x}=-1\\x+8=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}3x+8=-1\left(2-7x\right)\\x=0-8\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}3x+8=-2+7x\\x=-8\end{cases}\Leftrightarrow\orbr{\begin{cases}-4x=-10\\x=-8\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=\frac{5}{2}\\x=-8\end{cases}}}\) (nhận)
Vậy ......
d) (x+1)2-4(x2-2x+1) = 0
<=> x2+2x+1-4x2+8x-4 = 0
<=> -3x2+10x-3 = 0
giải phương trình
Bài 2:
a) ĐK: $x\geq \pm \frac{1}{2}; x\neq 0$
\(\left(\frac{2x+1}{2x-1}-\frac{2x-1}{2x+1}\right):\frac{4x}{10x-5}=\frac{(2x+1)^2-(2x-1)^2}{(2x-1)(2x+1)}.\frac{10x-5}{4x}\)
\(\frac{4x^2+4x+1-(4x^2-4x+1)}{(2x-1)(2x+1)}.\frac{5(2x-1)}{4x}=\frac{8x}{(2x-1)(2x+1)}.\frac{5(2x-1)}{4x}\)
\(=\frac{10}{2x+1}\)
b) ĐK : $x\neq 0;-1$
\(\left(\frac{1}{x^2+x}-\frac{2-x}{x+1}\right):\left(\frac{1}{x}+x-2\right)=\left(\frac{1}{x(x+1)}-\frac{x(2-x)}{x(x+1)}\right):\frac{1+x^2-2x}{x}\)
\(=\frac{1-2x+x^2}{x(x+1)}.\frac{x}{1+x^2-2x}=\frac{x}{x(x+1)}=\frac{1}{x+1}\)
Bài 3:
a) ĐKXĐ: \(x\neq \pm 1\)
b)
\(A=\left(\frac{x+1}{2x-2}-\frac{3}{1-x^2}-\frac{x+3}{2x+2}\right).\frac{4x^2-4}{5}\)
\(=\left[\frac{(x+1)^2}{2(x-1)(x+1)}+\frac{6}{2(x-1)(x+1)}-\frac{(x+3)(x-1)}{2(x+1)(x-1)}\right].\frac{4(x^2-1)}{5}\)
\(=\frac{(x+1)^2+6-(x^2+2x-3)}{2(x-1)(x+1)}.\frac{4(x-1)(x+1)}{5}\)
\(=\frac{10}{2(x-1)(x+1)}.\frac{4(x-1)(x+1)}{5}=4\)
a) ĐKXĐ: x∉{2;5}
Ta có: \(\frac{6x+1}{x^2-7x+10}+\frac{5}{x-2}=\frac{3}{x-5}\)
\(\Leftrightarrow\frac{6x+1}{\left(x-2\right)\left(x-5\right)}+\frac{5\left(x-5\right)}{\left(x-2\right)\left(x-5\right)}-\frac{3\left(x-2\right)}{\left(x-5\right)\left(x-2\right)}=0\)
\(\Leftrightarrow6x+1+5x-25-3\left(x-2\right)=0\)
\(\Leftrightarrow11x-24-3x+6=0\)
\(\Leftrightarrow8x-18=0\)
\(\Leftrightarrow8x=18\)
hay \(x=\frac{9}{4}\)(tm)
Vậy: \(x=\frac{9}{4}\)
b) ĐKXĐ: x∉{0;2;-2}
Ta có: \(\frac{2}{x^2-4}-\frac{x-1}{x\left(x-2\right)}+\frac{x-4}{x\left(x+2\right)}=0\)
\(\Leftrightarrow\frac{2x}{x\left(x-2\right)\left(x+2\right)}-\frac{\left(x-1\right)\left(x+2\right)}{x\left(x-2\right)\left(x+2\right)}+\frac{\left(x-4\right)\left(x-2\right)}{x\left(x+2\right)\left(x-2\right)}=0\)
\(\Leftrightarrow2x-\left(x^2+x-2\right)+x^2-6x+8=0\)
\(\Leftrightarrow2x-x^2-x+2+x^2-6x+8=0\)
\(\Leftrightarrow-5x+10=0\)
\(\Leftrightarrow-5x=-10\)
hay x=2(ktm)
Vậy: x∈∅
a)\(B=\left(\frac{x-2}{x^2+2x}+\frac{1}{x+2}\right).\frac{x+1}{x-1}=\left(\frac{x^2-2}{x^2+2x}+\frac{x}{x^2+2x}\right).\frac{x+1}{x-1}=\frac{x^2+x-2}{x^2+2x}.\frac{x+1}{x-1}\)
\(=\frac{x^2-x+2x-2}{x\left(x+2\right)}.\frac{x+1}{x-1}=\frac{x\left(x-1\right)+2\left(x-1\right)}{x\left(x+2\right)}.\frac{x+1}{x-1}=\frac{\left(x-1\right)\left(x+2\right)}{x\left(x+2\right)}.\frac{x+1}{x-1}=\frac{x+1}{x}\)
b)\(2B=2x+5\Leftrightarrow2.\frac{x+1}{x}=2x+5\Leftrightarrow\frac{2x+2}{x}=2x+5\Leftrightarrow2x+2=2x^2+5x\)
\(\Leftrightarrow0=2x^2+3x-2\Leftrightarrow2x^2+4x-x-2=0\Leftrightarrow2x\left(x+2\right)-\left(x+2\right)=0\)
\(\Leftrightarrow\left(2x-1\right)\left(x+2\right)=0\Leftrightarrow\orbr{\begin{cases}2x-1=0\\x+2=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=\frac{1}{2}\\x=-2\end{cases}}\)
cảm ơn bạn nhé