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27 tháng 7 2016
\(\left(2x-1\right)^2+\left(x+3\right)^2-5\left(x+7\right)\left(x-7\right)=0\)
\(=4x^2+1-4x+\left(x^2+9+6x\right)-5\left(x^2-7^2\right)=0\)
\(=4x^2+1-4x+x^2+9+6x-5x^2+245=0\)
\(=\left(4x^2+x^2-5x^2\right)-\left(4x-6x\right)+\left(1+9+245\right)=0\)
\(=2x+255=0\)
\(\Rightarrow2x=-255\)
\(x=-127,5\)
TN
27 tháng 7 2016
(2x-1)^2+(x+3)^2-5(x+7)(x-7)=0
=>4x2-4x+1+x2+6x+9+245-5x2=0
=>(4x2+x2-5x2)+(6x-4x)+(1+9+245)=0
=>2x+255=0
=>2x=-255 <=>x=-255/2
L
20 giờ trước (15:48)
a)
\(\left(x+2\right)^2-9=0\)
\(\Rightarrow\left(x+2\right)^2=9=3^2\)
\(\Rightarrow x+2=\pm3\)
\(\Rightarrow x=-5;1\)
b)
\(25x^2-10x+1=0\)
\(\left(5x\right)^2-2\cdot5x+1^2=0\)
\(\Rightarrow\left(5x+1\right)^2=0\)
\(\Rightarrow5x+1=0\)
\(\Rightarrow5x=-1;x=\dfrac{-1}{5}\)
c)
\(x^2+14x+49=0\)
\(\Rightarrow x^2+2\cdot7x+7^2=0\)
\(\Rightarrow\left(x+7\right)^2=0;x+7=0\)
\(\Rightarrow x=-7\)
d)
\(\left(2x-1\right)^2+\left(x+3\right)^2-5\left(x+7\right)\left(x-7\right)=0\)
\(4x^2-4x+1+x^2+6x+9-5x^2+5\cdot49=0\)
\(\Rightarrow5x^2-5x^2-4x+6x+10+245=0\)
\(\Rightarrow2x+255=0\)
\(\Rightarrow2x=-255\)
\(\Rightarrow x=\dfrac{-255}{2}\)
TM
3
9 tháng 7 2017
a/ (x-3)2 - 4 = 0
=> (x-3-2)(x-3+2)=0
=> (x-5)(x-1)=0
=> x = 5 hoặc x=1
17 tháng 11 2021
\(1,\Leftrightarrow x\left(x-9\right)=0\Leftrightarrow\left[{}\begin{matrix}x=9\\x=0\end{matrix}\right.\\ 2,\Leftrightarrow x^2-4x-x^2=7\Leftrightarrow-4x=7\Leftrightarrow x=-\dfrac{7}{4}\\ 3,\Leftrightarrow3x+2x-10=5\Leftrightarrow5x=15\Leftrightarrow x=3\\ 4,\Leftrightarrow\left(5x-1\right)\left(5x+1\right)=0\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{5}\\x=-\dfrac{1}{5}\end{matrix}\right.\\ 5,\Leftrightarrow\left(x-2\right)\left(3x-5\right)=0\Leftrightarrow\left[{}\begin{matrix}x=2\\x=\dfrac{5}{3}\end{matrix}\right.\\ 6,\Leftrightarrow\left(x-7\right)\left(3x+4\right)=0\Leftrightarrow\left[{}\begin{matrix}x=7\\x=-\dfrac{4}{3}\end{matrix}\right.\)
\(7,\Leftrightarrow\left(2x-3\right)\left(2x+3\right)=0\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\x=-\dfrac{3}{2}\end{matrix}\right.\\ 8,\Leftrightarrow\left(x-4\right)\left(10x+2\right)=0\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{1}{5}\\x=4\end{matrix}\right.\\ 9,\Leftrightarrow2x^2-5x-2x^2=0\Leftrightarrow x=0\\ 10,\Leftrightarrow2x\left(x-2\right)=0\Leftrightarrow\left[{}\begin{matrix}x=0\\x=2\end{matrix}\right.\\ 11,\Leftrightarrow\left(4x-3\right)\left(3-2x\right)=0\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{4}\\x=\dfrac{3}{2}\end{matrix}\right.\\ 12,\Leftrightarrow2x^2-10x-2x^2=3\Leftrightarrow-10x=3\Leftrightarrow x=-\dfrac{3}{10}\)
17 tháng 11 2021
\(1,\Leftrightarrow x\left(x-9\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x=9\end{matrix}\right.\\ 2,\Leftrightarrow x^2-4x-x^2=7\\ \Leftrightarrow-4x=7\\ \Leftrightarrow x=\dfrac{-7}{4}\\ 3,\Leftrightarrow3x+2x-10=5\\ \Leftrightarrow5x=15\\ \Leftrightarrow x=3\\ 4,\Leftrightarrow\left(5x-1\right)\left(5x+1\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{5}\\x=-\dfrac{1}{5}\end{matrix}\right.\)
\(5,\Leftrightarrow\left(x-2\right)\left(3x-5\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=2\\x=\dfrac{5}{3}\end{matrix}\right.\\ 6,\Leftrightarrow\left(3x+4\right)\left(x-7\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{4}{3}\\x=7\end{matrix}\right.\\ 7,\Leftrightarrow\left(2x-3\right)\left(2x+3\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\x=-\dfrac{3}{2}\end{matrix}\right.\)
\(8,\Leftrightarrow10x\left(x-4\right)+2\left(x-4\right)=0\\ \Leftrightarrow\left(x-4\right)\left(10x+2\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=4\\x=-\dfrac{1}{5}\end{matrix}\right.\\ 9,\Leftrightarrow2x^2-5x-2x^2=0\\ \Leftrightarrow-5x=0\\ \Leftrightarrow x=0\\ 10,\Leftrightarrow2x\left(x-2\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x=2\end{matrix}\right.\)
\(11,\Leftrightarrow\left(2x-3\right)\left(4x-3\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\x=\dfrac{3}{4}\end{matrix}\right.\\ 12,\Leftrightarrow2x^2-10x-2x^2=3\\ \Leftrightarrow-10x=3\\ \Leftrightarrow x=-\dfrac{3}{10}\)
PT
5
XO
11 tháng 8 2021
(x + 4)2 - (x + 1)(x - 1) = 16
=> x2 + 8x + 16 - x2 + 1 = 16
=> 8x + 17 = 16
=> 8x = -1
=> x = -1/8
b) (2x - 1)2 + (x - 3)2 - 5(x + 7)(x - 7) = 0
=> (4x2 - 4x + 1) + (x2 - 6x + 9) - 5(x2 - 49) = 0
=> 5x2 - 10x + 10 - 5x2 + 245 = 0
=> -10x + 255 = 0
=> 10x = 255
=> x = 25,5
Vậy x = 25,5
LT
3
CM
11 tháng 9 2019
a) x = 1; x = - 1 3 b) x = 2.
c) x = 3; x = -2. d) x = -3; x = 0; x = 2.
NT
2
12 tháng 7 2018
\(a,x^2-2x=24\)
\(x^2-2x-24=0\)
\(x^2-2x+1-25=0\)
\(\left(x-1\right)^2=5^2=\left(-5\right)^2\)
\(x-1=5\) hoặc \(x-1=-5\)
\(\Rightarrow\hept{\begin{cases}x=6\\x=-4\end{cases}}\)
\(b,\left(2x-1\right)^2+\left(x+3\right)^2-5\left(x+7\right)\left(x-7\right)=0\)
\(4x^2-4x+1+x^2+6x+9-5\left(x^2-49\right)=0\)
\(4x^2-4x+1+x^2+6x+9-5x^2+245=0\)
\(2x+255=0\)
\(2x=-255\)
\(x=-\frac{255}{2}\)
HH
11 tháng 7 2018
a/ \(x^2-2x=24\)
<=> \(x^2-2x+1-1=24\)
<=> \(\left(x-1\right)^2=25\)
<=> \(\orbr{\begin{cases}x-1=25\\x-1=-25\end{cases}}\)<=> \(\orbr{\begin{cases}x=26\\x=-24\end{cases}}\)
b/ \(\left(2x-1\right)^2+\left(x+3\right)^2-5\left(x+7\right)\left(x-7\right)=0\)
<=> \(4x^2-4x+1+x^2+6x+9-5\left(x^2-49\right)=0\)
<=> \(4x^2-4x+1+x^2+6x+9-5x^2+245=0\)
<=> \(2x+255=0\)
<=> \(2x=-255\)
<=> \(x=-\frac{255}{2}\)
(x-1)2+(x+3)2-5(x+7)(x-7)=0
\(\Leftrightarrow x^2-2x+1+x^2+6x+9-5\left(x^2-49\right)=0\)
\(\Leftrightarrow x^2-2x+1+x^2+6x+9-5x^2+245=0\)
\(\Leftrightarrow-3x^2+4x+255=0\)
\(\Leftrightarrow-3\left(x^2-\frac{4}{3}x\right)+255=0\)
\(\Leftrightarrow-3\left(x^2-2.x.\frac{2}{3}+\frac{4}{9}\right)+3.\frac{4}{9}+255=0\)
\(\Leftrightarrow-3\left(x-\frac{2}{3}\right)^2+\frac{769}{3}\)
\(\Leftrightarrow-3\left(x-\frac{2}{3}\right)^2=-\frac{769}{3}\)
\(\Leftrightarrow\left(x-\frac{2}{3}\right)^2=\frac{769}{9}\)
\(\Leftrightarrow\orbr{\begin{cases}x-\frac{2}{3}=\sqrt{\frac{769}{9}}\\x-\frac{2}{3}=-\sqrt{\frac{769}{9}}\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=\sqrt{\frac{769}{9}}+\frac{2}{3}=\frac{\sqrt{769}+2}{3}\\x=-\sqrt{\frac{769}{9}}+\frac{2}{3}=\frac{2-\sqrt{769}}{3}\end{cases}}\)
Vậy \(\Leftrightarrow\orbr{\begin{cases}x=\frac{\sqrt{769}+2}{3}\\x=\frac{2-\sqrt{769}}{3}\end{cases}}\)