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a) ĐKXĐ: x - 3 \(\ne\)0 x \(\ne\)3
9 - x2 \(\ne\)0 <=> x \(\ne\)\(\pm\)3
x + 3 \(\ne\)0 x \(\ne\)-3
\(\frac{6x-12}{2x^2-18}\) \(\ne\)0 \(6x-12\ne0\) và \(2x^2-18\ne0\)
x \(\ne\)\(\pm\)3
<=> \(x\ne2\) và x \(\ne\)\(\pm\)3
<=> x \(\ne\)\(\pm\)3 và x \(\ne\)2
Ta có: B = \(\left(\frac{x+3}{x-3}+\frac{2x^2-6}{9-x^2}+\frac{x}{x+3}\right):\frac{6x-12}{2x^2-18}\)
B = \(\left(\frac{\left(x+3\right)\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}-\frac{2x^2-6}{\left(x-3\right)\left(x+3\right)}+\frac{x\left(x-3\right)}{\left(x-3\right)\left(x+3\right)}\right):\frac{6\left(x-2\right)}{2\left(x^2-9\right)}\)
B = \(\left(\frac{x^2+6x+9-2x^2+6+x^2-3x}{\left(x-3\right)\left(x+3\right)}\right):\frac{3\left(x-2\right)}{\left(x-3\right)\left(x+3\right)}\)
B = \(\frac{3x+15}{\left(x+3\right)\left(x-3\right)}\cdot\frac{\left(x-3\right)\left(x+3\right)}{3\left(x-2\right)}\)
B = \(\frac{3\left(x+5\right)}{3\left(x-2\right)}\)
B = \(\frac{x+5}{x-2}\)
b) (sai đề)
c) Ta có: B = \(\frac{x+5}{x-2}=\frac{\left(x-2\right)+7}{x-2}=1+\frac{7}{x-2}\)
Để B \(\in\)Z <=> 7 \(⋮\)x - 2 <=> x - 2 \(\in\)Ư(7) = {1; -1; 7; -7}
Lập bảng:
| x - 2 | 1 | -1 | 7 | -7 |
| x | 3 (ktm) | 1 | 9 | -5 |
Vậy ...
a) \(\text{ĐKXĐ:}\hept{\begin{cases}x\ne\pm3\\x\ne2\end{cases}}\)
\(B=\left(\frac{x+3}{x-3}+\frac{2x^2-6}{9-x^2}+\frac{x}{x+3}\right):\frac{6x-12}{2x^2-18}\)
\(B=\left[\frac{x+3}{x-3}+\frac{2x^2-6}{\left(x-3\right)\left(x+3\right)}+\frac{x}{x+3}\right].\frac{2\left(x^2-9\right)}{6\left(x-2\right)}\)
\(B=\left[\frac{\left(x+3\right)\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}-\frac{2x^2-6}{\left(x-3\right)\left(x+3\right)}+\frac{x\left(x-3\right)}{\left(x-3\right)\left(x+3\right)}\right]\)
\(B=\left[\frac{x^2+6x+9}{\left(x-3\right)\left(x+3\right)}-\frac{2x^2-6}{\left(x-3\right)\left(x+3\right)}+\frac{x^2-3x}{\left(x-3\right)\left(x+3\right)}\right].\frac{2\left(x^2-9\right)}{6\left(x-2\right)}\)
\(B=\frac{x^2+6x+9-\left(2x^2-6\right)+x^2-3}{\left(x-3\right)\left(x+3\right)}.\frac{2\left(x^2-9\right)}{6\left(x-2\right)}\)
\(B=\frac{3\left(x+5\right)}{\left(x-3\right)\left(x+3\right)}.\frac{2\left(x-3\right)\left(x+3\right)}{6\left(x-2\right)}\)
\(B=\frac{x+5}{x-2}\)
b) Ta có: \(\frac{x+5}{x-2}=1+\frac{7}{x-2}\)
Để B nguyên thì: \(7⋮x-2\)
\(\Rightarrow x-2\inƯ\left(7\right)\)
\(\RightarrowƯ\left(7\right)=\left\{\pm1;\pm7\right\}\)
Ta có bảng:
| x - 2 | -1 | 1 | -7 | 7 |
| x | 1 | 3 (loại) | -5 | 9 |
Vậy: \(x\in\left\{1;-5;9\right\}\)
\(A=\dfrac{x^2+6x+9-2x^2+6+x^2-3x}{\left(x-3\right)\left(x+3\right)}\cdot\dfrac{2\left(x-3\right)\left(x+3\right)}{6\left(x-2\right)}\)
\(=\dfrac{3x+15}{\left(x-3\right)\left(x+3\right)}\cdot\dfrac{\left(x-3\right)\left(x+3\right)}{3\left(x-2\right)}=\dfrac{x+5}{x-2}\)
Bài 1:
a) Ta có: \(2,3x-2\left(0,7+2x\right)=3,6-1,7x\)
\(\Leftrightarrow2,3x-1,4-4x-3,6+1,7x=0\)
\(\Leftrightarrow-5=0\)(vl)
Vậy: \(x\in\varnothing\)
b) Ta có: \(\frac{4}{3}x-\frac{5}{6}=\frac{1}{2}\)
\(\Leftrightarrow\frac{4}{3}x=\frac{1}{2}+\frac{5}{6}=\frac{8}{6}=\frac{4}{3}\)
hay x=1
Vậy: x=1
c) Ta có: \(\frac{x}{10}-\left(\frac{x}{30}+\frac{2x}{45}\right)=\frac{4}{5}\)
\(\Leftrightarrow\frac{9x}{90}-\frac{3x}{90}-\frac{4x}{90}-\frac{72}{90}=0\)
\(\Leftrightarrow2x-72=0\)
\(\Leftrightarrow2\left(x-36\right)=0\)
mà 2>0
nên x-36=0
hay x=36
Vậy: x=36
d) Ta có: \(\frac{10x+3}{8}=\frac{7-8x}{12}\)
\(\Leftrightarrow12\left(10x+3\right)=8\left(7-8x\right)\)
\(\Leftrightarrow120x+36=56-64x\)
\(\Leftrightarrow120x+36-56+64x=0\)
\(\Leftrightarrow184x-20=0\)
\(\Leftrightarrow184x=20\)
hay \(x=\frac{5}{46}\)
Vậy: \(x=\frac{5}{46}\)
e) Ta có: \(\frac{10x-5}{18}+\frac{x+3}{12}=\frac{7x+3}{6}-\frac{12-x}{9}\)
\(\Leftrightarrow\frac{2\left(10x-5\right)}{36}+\frac{3\left(x+3\right)}{36}-\frac{6\left(7x+3\right)}{36}+\frac{4\left(12-x\right)}{36}=0\)
\(\Leftrightarrow2\left(10x-5\right)+3\left(x+3\right)-6\left(7x+3\right)+4\left(12-x\right)=0\)
\(\Leftrightarrow20x-10+3x+9-42x-18+48-4x=0\)
\(\Leftrightarrow-23x+29=0\)
\(\Leftrightarrow-23x=-29\)
hay \(x=\frac{29}{23}\)
Vậy: \(x=\frac{29}{23}\)
f) Ta có: \(\frac{x+4}{5}-x-5=\frac{x+3}{2}-\frac{x-2}{2}\)
\(\Leftrightarrow\frac{2\left(x+4\right)}{10}-\frac{10x}{10}-\frac{50}{10}=\frac{25}{10}\)
\(\Leftrightarrow2x+8-10x-50-25=0\)
\(\Leftrightarrow-8x-67=0\)
\(\Leftrightarrow-8x=67\)
hay \(x=\frac{-67}{8}\)
Vậy: \(x=\frac{-67}{8}\)
g) Ta có: \(\frac{2-x}{4}=\frac{2\left(x+1\right)}{5}-\frac{3\left(2x-5\right)}{10}\)
\(\Leftrightarrow5\left(2-x\right)-8\left(x+1\right)+6\left(2x-5\right)=0\)
\(\Leftrightarrow10-5x-8x-8+12x-30=0\)
\(\Leftrightarrow-x-28=0\)
\(\Leftrightarrow-x=28\)
hay x=-28
Vậy: x=-28
h) Ta có: \(\frac{x+2}{3}+\frac{3\left(2x-1\right)}{4}-\frac{5x-3}{6}=x+\frac{5}{12}\)
\(\Leftrightarrow\frac{4\left(x+2\right)}{12}+\frac{9\left(2x-1\right)}{12}-\frac{2\left(5x-3\right)}{12}-\frac{12x}{12}-\frac{5}{12}=0\)
\(\Leftrightarrow4x+8+18x-9-10x+6-12x-5=0\)
\(\Leftrightarrow0x=0\)
Vậy: \(x\in R\)
Bài 2:
a) Ta có: \(5\left(x-1\right)\left(2x-1\right)=3\left(x+8\right)\left(x-1\right)\)
\(\Leftrightarrow5\left(x-1\right)\left(2x-1\right)-3\left(x-1\right)\left(x+8\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left[5\left(2x-1\right)-3\left(x+8\right)\right]=0\)
\(\Leftrightarrow\left(x-1\right)\left(10x-5-3x-24\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(7x-29\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\7x-29=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\7x=29\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=\frac{29}{7}\end{matrix}\right.\)
Vậy: Tập nghiệm \(S=\left\{1;\frac{29}{7}\right\}\)
b) Ta có: \(\left(3x-2\right)\left(x+6\right)\left(x^2+5\right)=0\)(1)
Ta có: \(x^2\ge0\forall x\)
\(\Rightarrow x^2+5\ge5\ne0\forall x\)(2)
Từ (1) và (2) suy ra:
\(\left[{}\begin{matrix}3x-2=0\\x+6=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}3x=2\\x=-6\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{2}{3}\\x=-6\end{matrix}\right.\)
Vậy: Tập nghiệm \(S=\left\{\frac{2}{3};-6\right\}\)
c) Ta có: \(\left(3x-2\right)\left(9x^2+6x+4\right)-\left(3x-1\right)\left(9x^2-3x+1\right)=x-4\)
\(\Leftrightarrow27x^3-8-\left(27x^3-1\right)-x+4=0\)
\(\Leftrightarrow27x^3-8-27x^3+1-x+4=0\)
\(\Leftrightarrow-x-3=0\)
\(\Leftrightarrow-x=3\)
hay x=-3
Vậy: Tập nghiệm S={-3}
d) Ta có: \(x\left(x-1\right)-\left(x-3\right)\left(x+4\right)=5x\)
\(\Leftrightarrow x^2-x-\left(x^2+x-12\right)-5x=0\)
\(\Leftrightarrow x^2-x-x^2-x+12-5x=0\)
\(\Leftrightarrow12-7x=0\)
\(\Leftrightarrow7x=12\)
hay \(x=\frac{12}{7}\)
Vậy: Tập nghiệm \(S=\left\{\frac{12}{7}\right\}\)
e) Ta có: (2x+1)(2x-1)=4x(x-7)-3x
\(\Leftrightarrow4x^2-1-4x^2+28x+3x=0\)
\(\Leftrightarrow31x-1=0\)
\(\Leftrightarrow31x=1\)
hay \(x=\frac{1}{31}\)
Vậy: Tập nghiệm \(S=\left\{\frac{1}{31}\right\}\)
a) \(\frac{x+3}{x-2}-\frac{2x+3}{x+2}=\frac{2x^2+5x+12}{x^2-4}\)
ĐKXĐ: \(\left\{\begin{matrix}x\ne2\\x\ne-2\end{matrix}\right.\)
\(\Rightarrow\left(x+3\right)\left(x+2\right)-\left(2x+3\right)\left(x-2\right)=2x^2+5x+12\)
\(\Leftrightarrow x^2+2x+3x+6-2x^2+4x-3x+6-2x^2-5x-12=0\)
\(\Leftrightarrow-3x^2+4x=0\)
\(\Leftrightarrow3x^2-4x=0\)
\(\Leftrightarrow x\left(3x-4\right)=0\)
\(\Leftrightarrow\left[\begin{matrix}x=0\\3x-4=0\end{matrix}\right.\Leftrightarrow\left[\begin{matrix}x=0\\3x=4\end{matrix}\right.\Leftrightarrow\left[\begin{matrix}x=0\left(tmđk\right)\\x=\frac{4}{3}\left(tmđk\right)\end{matrix}\right.\)
Vậy: \(x=0;\frac{4}{3}\)
_Chúc bạn học tốt_
b) Ta có: \(\frac{2x+5}{x-3}+\frac{x-1}{x+3}=\frac{x^2+6x+18}{x^2-9}\)
ĐKXĐ: \(\left\{\begin{matrix}x\ne3\\x\ne-3\end{matrix}\right.\)
\(\Leftrightarrow\frac{\left(2x+5\right)\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}+\frac{\left(x-1\right)\left(x-3\right)}{\left(x+3\right)\left(x-3\right)}=\frac{x^2+6x+18}{\left(x+3\right)\left(x-3\right)}\)
\(\Rightarrow\left(2x+5\right)\left(x+3\right)+\left(x-1\right)\left(x-3\right)=x^2+6x-18\)
\(\Leftrightarrow2x^2+6x+5x+15+x^2-3x-x+3-x^2-6x-18=0\)
\(\Leftrightarrow2x^2+x=0\)
\(\Leftrightarrow x\left(2x+1\right)=0\)
\(\Leftrightarrow\left[\begin{matrix}x=0\\2x+1=0\end{matrix}\right.\Leftrightarrow\left[\begin{matrix}x=0\\2x=-1\end{matrix}\right.\Leftrightarrow\left[\begin{matrix}x=0\\x=-\frac{1}{2}\end{matrix}\right.\)
Vậy: \(x=0;-\frac{1}{2}\)
_Chúc bạn học tốt_
\(\frac{x-3}{5}-\frac{2x-1}{10}=\frac{x+1}{2}+\frac{1}{4}\)
\(< =>\frac{\left(x-3\right).4}{20}-\frac{\left(2x-1\right).2}{20}=\frac{\left(x+1\right).10}{20}+\frac{5}{20}\)
\(< =>4x-12-4x+2=10x+10+5\)
\(< =>10x=-10-10-5=-25\)
\(< =>x=-\frac{25}{10}=-\frac{5}{2}\)
\(\frac{x+3}{2}-\frac{2x-1}{3}-1=\frac{x+5}{5}\)
\(< =>\frac{\left(x+3\right).15}{30}-\frac{\left(2x-1\right).10}{30}-\frac{30}{30}=\frac{\left(x+5\right).5}{30}\)\(< =>15x+45-20x+10-30=5x+25\)
\(< =>-5x+25=5x+25< =>10x=0< =>x=0\)
\(C=\frac{\left(x+3\right)^2-2x^2+6+x\left(x-3\right)}{x^2-9}.\frac{2x^2-18}{6x-12}\)\(\)
\(C=\frac{x^2+6x+9-2x^2+6+x^2-3x}{x^2-9}.\frac{2\left(x^2-9\right)}{6x-12}\)\(C=\frac{3x+15}{6x-12}.2=\frac{x+5}{x-2}=1+\frac{7}{x-2}\)
Để C nguyên =>(x-2) thuộc Ư(7) \(\Rightarrow x\in\left\{3;1;9;-5\right\}\)