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12 tháng 7 2016
a. \(x\left(x^2-25\right)-\left(x^3-2x^2+4x+2x^2-4x+8\right)=17\)
\(x^3-25x-\left(x^3+8\right)=17\)
\(x^3-25x-x^3-8=17\)
\(-25x=25\)
\(x=-1\)
12 tháng 7 2016
c. \(6x^2-\left(6x^2-4x+15x-10\right)=7\)
\(6x^2-6x^2-11x+10=7\)
\(-11x=-3\)
\(x=\frac{3}{11}\)
14 tháng 8 2019
a) (x - 2)(x + 3) = 6
=> x2 + 3x - 2x - 6 = 6
=> x2 + x - 6 - 6 = 0
=> x2 + x - 12 = 0
=> x2 + 4x - 3x - 12 = 0
=> x(x + 4) - 3(x + 4) = 0
=> (x - 3)(x + 4) = 0
=> \(\orbr{\begin{cases}x-3=0\\x+4=0\end{cases}}\)
=> \(\orbr{\begin{cases}x=3\\x=-4\end{cases}}\)
b) (2x - 3)(x + 2) = 4
=> 2x2 + 4x - 3x - 6 = 4
=> 2x2 + x - 6 - 4 = 0
=> 2x2 + x - 10 = 0
=> 2x2 + 5x - 4x - 10 = 0
=> x(2x + 5) - 2(2x + 5) = 0
=> (x - 2)(2x + 5) = 0
=> \(\orbr{\begin{cases}x-2=0\\2x+5=0\end{cases}}\)
=> \(\orbr{\begin{cases}x=2\\x=-\frac{5}{2}\end{cases}}\)
16 tháng 8 2016
a) \(x\left(x-4\right)-\left(x^2-8\right)=0\)
\(\Leftrightarrow x^2-4x-x^2+8=0\)
\(\Leftrightarrow-4\left(x-2\right)=0\)
\(\Leftrightarrow x-2=0\)
\(\Leftrightarrow x=2\)
b) \(\left(3x+2\right)\left(x-1\right)-3\left(x+1\right)\left(x-2\right)=4\)
\(\Leftrightarrow3x^2-3x+2x-2-3\left(x^2-2x+x-2\right)=0\)
\(\Leftrightarrow3x^2-3x+2x-2-3x^2+6x-3x+6=0\)
\(\Leftrightarrow2x=-4\)
\(\Leftrightarrow x=-2\)
c) \(x\left(x+5\right)\left(x-5\right)-\left(x+2\right)\left(x^2-2x+4\right)=17\)
\(\Leftrightarrow x\left(x^2-25\right)-\left(x^3+8\right)=17\)
\(\Leftrightarrow x^3-25x-x^3-8=17\)
\(\Leftrightarrow-25x=25\)
\(\Leftrightarrow x=-1\)
16 tháng 8 2016
a) x(x - 4 ) - ( x^2 - 8 ) = 0
=>x2-4x-x2+8=0
=>8-4x=0
=>4x=8
=>x=2
b) ( 3x + 2 )( x - 1 ) - 3( x + 1 )( x - 2 ) = 4
=>3x2-x-2-3x2+3x+6=4
=>2x+4=4
=>2x=0
=>x=0
c) x( x + 5 )( x - 5 ) - ( x + 2 )( x^2 - 2x + 4 ) = 17
=>x(x2-25)-(x3+8)=17
=>x3-25x-x3-8=17
=>-25x-8=17
=>-25x=25
=>x=-1
TN
18 tháng 3 2020
\(a.\frac{4x-3}{x-5}=\frac{29}{3}\\ \Leftrightarrow\frac{3\left(4x-3\right)}{3\left(x-5\right)}=\frac{29\left(x-5\right)}{3\left(x-5\right)}\\ \Leftrightarrow3\left(4x-3\right)=29\left(x-5\right)\\ \Leftrightarrow3\left(4x-3\right)-29\left(x-5\right)=0\\ \Leftrightarrow12x-9-29x+145=0\\ \Leftrightarrow-17x+136=0\\ \Leftrightarrow-17x=-136\\ \Leftrightarrow x=\frac{-136}{-17}=8\)
\(b.\frac{2x-1}{5-3x}=2\\ \Leftrightarrow\frac{2x-1}{5-3x}=\frac{4}{2}\\ \Leftrightarrow\frac{2\left(2x-1\right)}{2\left(5-3x\right)}=\frac{4\left(5-3x\right)}{2\left(5-3x\right)}\\ \Leftrightarrow2\left(2x-1\right)=4\left(5-3x\right)\\ \Leftrightarrow2\left(2x-1\right)-4\left(5-3x\right)=0\\ \Leftrightarrow4x-2-20+12x=0\\ \Leftrightarrow16x-22=0\\ \Leftrightarrow16x=22\\ \Leftrightarrow x=\frac{22}{16}=\frac{11}{8}\)
\(c.\frac{4x-5}{x-1}=\frac{2+x}{x-1}\\ \Leftrightarrow4x-5=2+x\\ \Leftrightarrow4x-5-2-x=0\\ \Leftrightarrow3x-7=0\\ \Leftrightarrow3x=7\\ \Leftrightarrow x=\frac{7}{3}\)
TN
18 tháng 3 2020
\(d.\frac{7}{x+2}=\frac{3}{x-5}\\ \Leftrightarrow\frac{7\left(x-5\right)}{\left(x+2\right)\left(x-5\right)}=\frac{3\left(x+2\right)}{\left(x+2\right)\left(x-5\right)}\\ \Leftrightarrow7\left(x-5\right)=3\left(x+2\right)\\ \Leftrightarrow7\left(x-5\right)-3\left(x+2\right)=0\\ \Leftrightarrow7x-35-3x-6=0\\ \Leftrightarrow4x-41=0\\ \Leftrightarrow4x=41\\ \Leftrightarrow x=\frac{41}{4}\)
\(e.\frac{2x+5}{2x}-\frac{x}{x+5}=0\\ \Leftrightarrow\frac{\left(2x+5\right)\left(x+5\right)}{2x\left(x+5\right)}-\frac{x.2x}{2x\left(x+5\right)}=0\\ \Leftrightarrow\left(2x+5\right)\left(x+5\right)-2x^2=0\\ \Leftrightarrow2x^2+10x+5x+25-2x^2=0\\ \Leftrightarrow15x+25=0\\ \Leftrightarrow15x=-25\\ \Leftrightarrow x=\frac{-25}{15}=\frac{-5}{3}\)
\(f.\frac{12x+1}{11x-4}+\frac{10x-4}{9}=\frac{20x+17}{18}\\\Leftrightarrow\frac{18\left(12x+1\right)}{18\left(11x-4\right)}+\frac{\left(10x-4\right).2\left(11x-4\right)}{9.2\left(11x-4\right)}=\frac{\left(20x+17\right)\left(11x-4\right)}{18\left(11x-4\right)}\\ \Leftrightarrow18\left(12x+1\right)+\left(10x-4\right).2\left(11x-4\right)=\left(20x+17\right)\left(11x-4\right)\\ \Leftrightarrow220x^2+48x+50=220x^2+107x-68\\ \Leftrightarrow48x+50=107x-68\\ \Leftrightarrow48x-107x=-68-50\\ \Leftrightarrow59x=-118\\ \Leftrightarrow x=-2\)
24 tháng 7 2019
a) (x - 1)3 + (2 - x)(4 + 2x + x2) + 3x(x + 2) = 12
<=> x3 - 2x2 + x - x2 + 2x - 1 + 8 + 4x + 2x2 - 4x - 2x2 + 3x2 + 6x = 17
<=> 9x + 7 = 17
<=> 9x = 17 - 7
<=> 9x = 10
<=> x = \(\frac{10}{9}\)
b) (x + 2)(x2 - 2x + 4) - x(x2 - 2) = 15
<=> x3 - 2x2 + 4x + 2x2 - 4x + 8 - x3 + 2x = 15
<=> 2x + 8 = 15
<=> 2x = 15 - 8
<=> 2x = 7
<=> x = \(\frac{7}{2}\)
c) (x - 3)3 - (x - 3)(x2 + 3x + 9) + 9(x2 + 1)2 = 15
<=> x3 + 45x - 18 - x3 - 3x2 - 9x + 3x2 + 9x + 27 = 15
<=> 45x + 9 = 15
<=> 45x = 15 - 9
<=> 45x = 6
<=> x = \(\frac{6}{45}\)
d) x(x - 5)(x + 5) - (x + 2)(x2 - 2x + 4) = 3
<=> x3 - 25x - x3 + 2x2 - 4x - 8 = 3
<=> -25x - 8 = 3
<=> -25x = 3 + 8
<=> -25x = 11
<=> x = \(-\frac{11}{25}\)
7 tháng 7 2015
a. x=4,49
b. ko có giá trị của x
c. x=-0,44
d. x=-2+can3 ; x=-2-can3
TN
15 tháng 10 2017
\(a,\left(x+1\right)^3+\left(2-x\right)\left(4+2x+x^2\right)+3x\left(x+2\right)=17\)\(\Leftrightarrow x^3+3x^2+3x+1+8-x^3+3x^2+6x-17=0\)\(\Leftrightarrow6x^2+9x-8=0\)
\(\Leftrightarrow x^2+\dfrac{3}{2}x-\dfrac{4}{3}=0\)
\(\Leftrightarrow\left(x^2+\dfrac{3}{2}x+\dfrac{9}{16}\right)-\dfrac{9}{16}-\dfrac{4}{3}=0\)
\(\Leftrightarrow\left(x+\dfrac{3}{4}\right)^2=\dfrac{91}{48}\)
\(\Leftrightarrow\left[{}\begin{matrix}x+\dfrac{3}{4}=\sqrt{\dfrac{91}{48}}\\x+\dfrac{3}{4}=-\sqrt{\dfrac{91}{48}}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\sqrt{\dfrac{91}{48}}-\dfrac{3}{4}\\x=-\sqrt{\dfrac{91}{48}}-\dfrac{3}{4}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-9+\sqrt{273}}{12}\\x=-\dfrac{9+\sqrt{273}}{12}\end{matrix}\right.\)
b, \(\left(x+2\right)\left(x^2-2x+4\right)-x\left(x^2-2\right)=15\)
\(\Leftrightarrow x^3+8-x^3+2x-15=0\)
\(\Leftrightarrow2x=7\Rightarrow x=\dfrac{7}{2}\)
\(x\left(x+5\right)\left(x-5\right)-\left(x+2\right)\left(x^2-2x+4\right)=17\)
\(\Leftrightarrow x\left(x^2-25\right)-\left(x^3+8\right)=17\)
\(\Leftrightarrow x^3-25x-x^3-8=17\)
\(\Leftrightarrow-25x=25\)
\(\Leftrightarrow x=25:-25\)
\(\Leftrightarrow x=-1\)
c) \(x\left(x+5\right)\left(x-5\right)-\left(x+2\right)\left(x^2-2x+4\right)=17\)
\(\Leftrightarrow x\left(x^2-25\right)-\left(x^3+8\right)=17\)
\(\Leftrightarrow x^3-25x-x^3-8=17\)
\(\Leftrightarrow-25x=25\)
\(\Leftrightarrow x=-1\)