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1. \(\left(4x+7\right)\left(3x+4\right)=\left(12x-5\right)\left(x-1\right)\)
\(12x^2+16x+21x+28=12x^2-12x-5x+5\)
\(12x^2+37x+28-12x^2+17x-5=0\)
54x+23=0
54x=-23
x=-23/54
2. \(\left(5x-1\right)\left(3x-1\right)=\left(5x-7\right)\left(3x+2\right)\)
\(15x^2-5x-3x+1=15x^2+10x-21x-14\)
\(15x^2-8x+1-15x^2+11x+14=0\)
3x+15=0
3x=-15
x=-5
Bài làm
a) \(\frac{3x+2}{3x-2}-\frac{6}{2+3x}=\frac{9x^2}{9x-4}\)
\(\Leftrightarrow\frac{3x+2}{3x-2}-\frac{6}{3x+2}=\frac{9x^2}{\left(3x-2\right)\left(3x+2\right)}\)
\(\Leftrightarrow\frac{(3x+2)\left(3x+2\right)}{(3x-2)\left(3x+2\right)}-\frac{6\left(3x-2\right)}{(3x+2)\left(3x-2\right)}=\frac{9x^2}{\left(3x-2\right)\left(3x+2\right)}\)
\(\Rightarrow\left(3x+2\right)^2-\left(18x-12\right)=9x^2\)
\(\Leftrightarrow9x^2+12x+4-18x+12x-9x^2=0\)
\(\Leftrightarrow6x+4=0\)
\(\Leftrightarrow x=-\frac{4}{6}\)
\(\Leftrightarrow x=-\frac{2}{3}\)
Vậy x = -2/3 là nghiệm.
@Tao Ngu :))@ 9x-4 không tách thành (3x+4)(3x-4) được đâu bạn. Chỗ đó phải là: 9x2-4
Bài thiếu đkxđ của x \(\hept{\begin{cases}3x-2\ne0\\2+3x\ne0\end{cases}\Leftrightarrow\hept{\begin{cases}3x\ne2\\3x\ne-2\end{cases}\Leftrightarrow}\hept{\begin{cases}x\ne\frac{2}{3}\\x\ne\frac{-2}{3}\end{cases}\Leftrightarrow}x\ne\pm\frac{2}{3}}\)
Bài 1 :
a, Ta có : \(\frac{x}{3}-\frac{2x+1}{2}=\frac{5x}{6}\)
=> \(\frac{2x}{6}-\frac{3\left(2x+1\right)}{6}=\frac{5x}{6}\)
=> \(2x-3\left(2x+1\right)=5x\)
=> \(2x-6x-3-5x=0\)
=> \(-9x=3\)
=> \(x=-\frac{1}{3}\)
Vậy phương trình trên có nghiệm là \(S=\left\{-\frac{1}{3}\right\}\)
b, Ta có : \(\frac{2x-1}{3}-\frac{5x+2}{4}=2x\)
=> \(\frac{4\left(2x-1\right)}{12}-\frac{3\left(5x+2\right)}{12}=2x\)
=> \(4\left(2x-1\right)-3\left(5x+2\right)=24x\)
=> \(8x-4-15x-6-24x=0\)
=> \(-31x=10\)
=> \(x=-\frac{10}{31}\)
Vậy phương trình trên có tập nghiệm là \(S=\left\{-\frac{10}{31}\right\}\)
c, - ĐKXĐ : \(x\ne\pm3\)
Ta có : \(\frac{6-x}{x^2-9}+\frac{2}{x+3}=-\frac{5}{x-3}\)
=> \(\frac{6-x}{x^2-9}+\frac{2\left(x-3\right)}{x^2-9}=-\frac{5\left(x+3\right)}{x^2-9}\)
=> \(6-x+2\left(x-3\right)=-5\left(x+3\right)\)
=> \(6-x+2x-6+5x+15=0\)
=> \(6x=-15\)
=> \(x=-\frac{15}{6}\) ( TM )
Vậy phương trình trên có tập nghiệm là \(S=\left\{-\frac{15}{6}\right\}\)
d, Ta có : \(\left(5x+2\right)\left(x-7\right)=0\)
=> \(\left[{}\begin{matrix}5x+2=0\\x-7=0\end{matrix}\right.\)
=> \(\left[{}\begin{matrix}x=-\frac{2}{5}\\x=7\end{matrix}\right.\)
Vậy phương trình trên có tập nghiệm là \(S=\left\{-\frac{2}{5};7\right\}\)
a) Ta có: \(\frac{3x-2}{6}-\frac{4-3x}{18}=\frac{4-x}{9}\)
\(\Leftrightarrow\frac{3\left(3x-2\right)}{18}-\frac{4-3x}{18}-\frac{2\left(4-x\right)}{18}=0\)
\(\Leftrightarrow9x-6-4+3x-\left(8-2x\right)=0\)
\(\Leftrightarrow12x-10-8+2x=0\)
\(\Leftrightarrow10x-18=0\)
\(\Leftrightarrow10x=18\)
hay \(x=\frac{9}{5}\)
Vậy: \(x=\frac{9}{5}\)
b) Ta có: \(\frac{2+3x}{6}-x+2=\frac{x-7}{9}\)
\(\Leftrightarrow\frac{3\left(2+3x\right)}{18}-\frac{18x}{18}+\frac{36}{18}-\frac{2\left(x-7\right)}{18}=0\)
\(\Leftrightarrow6+9x-18x+36-\left(2x-14\right)=0\)
\(\Leftrightarrow42-9x-2x+14=0\)
\(\Leftrightarrow56-11x=0\)
\(\Leftrightarrow11x=56\)
hay \(x=\frac{56}{11}\)
Vậy: \(x=\frac{56}{11}\)
c) ĐKXĐ: x∉{3;-3}
Ta có: \(\frac{6-x}{x^2-9}+\frac{2}{x+3}=\frac{-5}{x-3}\)
\(\Leftrightarrow\frac{6-x}{\left(x-3\right)\left(x+3\right)}+\frac{2\left(x-3\right)}{\left(x+3\right)\left(x-3\right)}=\frac{-5\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}\)
\(\Leftrightarrow6-x+2x-6=-5x-15\)
\(\Leftrightarrow x+5x+15=0\)
\(\Leftrightarrow6x=-15\)
hay \(x=\frac{-5}{2}\)(tm)
Vậy: \(x=\frac{-5}{2}\)
d) Ta có: \(\left(5x+2\right)\left(x^2-7\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}5x+2=0\\x^2-7=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}5x=-2\\x^2=7\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{-2}{5}\\x=\pm\sqrt{7}\end{matrix}\right.\)
Vậy: \(x\in\left\{\frac{-2}{5};\sqrt{7};-\sqrt{7}\right\}\)
e) ĐKXĐ: x∉{4;-4}
Ta có: \(\frac{3}{x-4}+\frac{5x-2}{x^2-16}=\frac{4}{x+4}\)
\(\Leftrightarrow\frac{3\left(x+4\right)}{\left(x-4\right)\left(x+4\right)}+\frac{5x-2}{\left(x-4\right)\left(x+4\right)}-\frac{4\left(x-4\right)}{\left(x-4\right)\left(x+4\right)}=0\)
\(\Leftrightarrow3x+12+5x-2-\left(4x-16\right)=0\)
\(\Leftrightarrow8x+10-4x+16=0\)
\(\Leftrightarrow4x+26=0\)
\(\Leftrightarrow4x=-26\)
hay \(x=\frac{-13}{2}\)(tm)
Vậy: \(x=\frac{-13}{2}\)
a) \(\frac{x+5}{4}\)-\(\frac{2x-5}{3}\)=\(\frac{6x-1}{3}\)+\(\frac{2x-3}{12}\)
⇔\(\frac{3\left(x+5\right)}{12}\)-\(\frac{4\left(2x-5\right)}{12}\)=\(\frac{4\left(6x-1\right)}{12}\)+\(\frac{2x-3}{12}\)
⇒ 3x+15-8x+20=24x-4+2x-3
⇔3x+15-8x+20-24x+4-2x+3=0
⇔-31x+42=0
⇔x=\(\frac{42}{31}\)
Vậy tập nghiệm của phương trình đã cho là:S={\(\frac{42}{31}\)}
a, \(\frac{x}{3}-\frac{5x}{6}=\frac{x}{4-5}\)
\(\Leftrightarrow\frac{2x}{6}-\frac{5x}{6}=\frac{x}{-1}\Leftrightarrow\frac{-x}{2}=\frac{x}{-1}\)
\(\Leftrightarrow x=2x\Leftrightarrow x-2x=0\Leftrightarrow x\left(1-2\right)=0\Leftrightarrow x=0\)
b, \(\frac{8x-3}{4}-\frac{3x-2}{2}=\frac{2x-1}{1}+\frac{x+3}{4}\)
\(\Leftrightarrow\frac{8x-3-6x+4}{4}=\frac{8x-4+x+3}{4}\)
Khử mẫu : \(2x+1=9x-1\Leftrightarrow-7x=-2\Leftrightarrow x=\frac{2}{7}\)
\(\frac{5x+1}{x^2+5}+\frac{5x+2}{x^2+4}+\frac{5x+3}{x^2+3}+\frac{5x+4}{x^2+2}=-4\)
\(\Leftrightarrow\frac{5x+1}{x^2+5}+1+\frac{5x+2}{x^2+4}+1+\frac{5x+3}{x^2+3}+1+\frac{5x+4}{x^2+2}+1=0\)
\(\Leftrightarrow\frac{x^2+5x+6}{x^2+5}+\frac{x^2+5x+6}{x^2+4}+\frac{x^2+5x+6}{x^2+3}+\frac{x^2+5x+6}{x^2+2}=0\)
\(\Leftrightarrow\left(x^2+5x+6\right)\left(\frac{1}{x^2+5}+\frac{1}{x^2+4}+\frac{1}{x^2+3}+\frac{1}{x^2+2}\right)=0\)
\(\Leftrightarrow x^2+5x+6=0\)\(\left(\text{Vì }\frac{1}{x^2+5}+\frac{1}{x^2+4}+\frac{1}{x^2+3}+\frac{1}{x^2+2}\ne0\forall x\right)\)
\(\Leftrightarrow\left(x+3\right)\left(x+2\right)=0\Leftrightarrow\left[{}\begin{matrix}x+3=0\\x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-3\\x=-2\end{matrix}\right.\)
Vậy phương trình có tập nghiệm \(S=\left\{-3;-2\right\}.\)
thankiu bạn nha!