Tìm x:
3x- 5= -7- 13
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\(\dfrac{x}{2}-\left(\dfrac{3x}{5}-\dfrac{13}{5}\right)=\dfrac{7}{5}+\dfrac{7}{10}x\\ \Rightarrow\dfrac{x}{2}-\dfrac{3x}{5}+\dfrac{13}{5}=\dfrac{7}{5}+\dfrac{7x}{10}\\ \Rightarrow\dfrac{5x}{10}-\dfrac{6x}{10}+\dfrac{26}{10}=\dfrac{14}{10}+\dfrac{7x}{10}\\ \Rightarrow\dfrac{5x}{10}-\dfrac{6x}{10}-\dfrac{7x}{10}=\dfrac{14}{10}-\dfrac{26}{10}\\ \Rightarrow\dfrac{-8x}{10}=-\dfrac{12}{10}\\ \Rightarrow\dfrac{-4x}{5}=-\dfrac{6}{5}\\ \Rightarrow-20x=-30\\ \Rightarrow x=\dfrac{3}{2}\)
\(\frac{x}{2}-\left(\frac{3x}{5}-\frac{13}{5}\right)=-\left(\frac{7}{5}+\frac{7}{10}.x\right)\)
\(\frac{x}{2}-\frac{3x-13}{5}=-\frac{14+7x}{10}\)
\(\frac{5x}{10}-\frac{2\left(3x-13\right)}{10}=-\frac{14+7x}{10}\)
\(\frac{5x-6x-26}{10}=\frac{-14-7x}{10}\)
\(\Rightarrow10.\left(5x-6x-26\right)=\left(-14-7x\right).10\)
\(\Rightarrow50x-60x-260=-140-70x\)
\(\Rightarrow-10x-260=-140-70x\)
\(\Rightarrow-10x+70x=-140+260\)
\(\Rightarrow60x=120\)
\(\Rightarrow x=2\)
\(\frac{x}{2}-\left(\frac{3x}{5}-\frac{13}{5}\right)=-\left(\frac{7}{5}+\frac{7}{10}x\right)\)
\(\Leftrightarrow\frac{x}{2}-\frac{3x}{5}+\frac{13}{5}=-\frac{7}{5}-\frac{7}{10}x\)
\(\Leftrightarrow\frac{x}{2}-\frac{3x}{5}=-\frac{7}{10}x-4\)
\(\Leftrightarrow-\frac{7}{10}x-\frac{x}{2}+\frac{3x}{5}=4\)
\(\Leftrightarrow x\left(-\frac{7}{10}-\frac{1}{2}+\frac{3}{5}\right)=4\)
\(\Leftrightarrow x\left(-\frac{3}{5}\right)=4\)
\(\Leftrightarrow x=-\frac{20}{3}\)
\(\dfrac{3x-5}{7}=\dfrac{2x+1}{13}\)
Ta có: \(\left(3x-5\right).13=\left(2x+1\right).7\)
\(=>39x-65=14x+7\)
\(=>39x-14x=7+65\)
\(=>25x=72\)
\(=>x=72:25\)
Vậy \(x=\dfrac{72}{25}\)
(* Công thức: Hai phân số bằng nhau thì hai nhân chéo cũng bằng nhau )
(3x - 5)/7 = (2x + 1)/13
13.(3x - 5) = 7.(2x + 1)
39x - 65 = 14x + 7
39x - 14x = 7 + 65
25x = 72
x = 72/25
a, \(\left(3x-5\right)\left(x+1\right)-\left(3x-1\right)\left(x+1\right)=x-4\)
\(\Leftrightarrow\left(x+1\right)\left(3x-5-3x+1\right)=x-4\Leftrightarrow-4\left(x+1\right)=x-4\)
\(\Leftrightarrow-4x-4=x-4\Leftrightarrow-4x-x=0\Leftrightarrow x=0\)
b, \(\left(x-2\right)\left(x+3\right)-\left(x+4\right)\left(x-7\right)=5-x\)
\(\Leftrightarrow x^2+x-6-x^2-3x+28=5-x\Leftrightarrow-2x+22=5-x\Leftrightarrow x=17\)
c, thiếu đề
d, \(3\left(x-7\right)\left(x+7\right)-\left(x-1\right)\left(3x+2\right)=13\)
\(\Leftrightarrow3x^2-147-3x^2+x+2=13\Leftrightarrow x=11+147=158\)
a.\(3x^2-2x-5-\left(3x^2+2x-1\right)=x-4\)
\(\Leftrightarrow-5x=0\Leftrightarrow x=0\)
b.\(x^2+x-6-\left(x^2-3x-28\right)=5-x\)
\(\Leftrightarrow5x=-17\Leftrightarrow x=-\frac{17}{5}\)
c.\(5\left(x^2-10x+21\right)-\left(5x^2-9x-2\right)=0\)
\(\Leftrightarrow-41x+107=0\Leftrightarrow x=\frac{107}{41}\)
d.\(3\left(x^2-49\right)-\left(3x^2-x-2\right)=13\Leftrightarrow x=158\)
x | x<-7/3 | -7/3</x<-5/2 | x>/-5/2 |
|2x+5| | -2x-5 | -2x-5 | 2x+5 |
|3x+7| | -3x-7 | 3x+7 | 3x+7 |
VT=VP | -5x-12=13/12 x x=-144/73 loại | x+2=13/12x x=24 loại | 5x+12=13/12 x x=-144/47 loại |
Vậy không có x nào thỏa mãn
\(3x-5=-7-13\)
\(\Rightarrow3x-5=-20\)
\(\Rightarrow3x=(-20)+5\)
\(\Rightarrow3x=-15\)
\(\Rightarrow x=-5\)
b) \(3\left(x-7\right)\left(x+7\right)-\left(x-1\right)\left(3x+2\right)=13\)
\(\Leftrightarrow\)\(3\left(x^2-49\right)-\left(3x^2-x-2\right)=13\)
\(\Leftrightarrow\)\(3x^2-147-3x^2+x+2=13\)
\(\Leftrightarrow\)\(x-145=13\)
\(\Leftrightarrow\)\(x=158\)
\(\text{3x- 5= -7- 13}\)
\(3x-5=-20\)
\(3x=-20+5\)
\(3x=-15\)
\(\Rightarrow x=-5\)
3x - 5 = -7 - 13
<=> 3x = -7 - 13 + 5
<=> 3x = -15
<=> x = -5
Vậy......