CD
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K
Khách
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DG
2
UV
11 tháng 12 2018
c, \(\left(x-\dfrac{1}{2}\right)^2=0\)
<=>x-\(\dfrac{1}{2}\)=0
<=> x=\(\dfrac{1}{2}\)
6 tháng 12 2022
a: =>x(x^2-13)=0
=>\(x\in\left\{0;\sqrt{13};-\sqrt{13}\right\}\)
b: =>25x^2=2
=>x^2=2/25
hay \(x=\pm\dfrac{\sqrt{2}}{5}\)
SG
2
20 tháng 4 2017
Bài giải:
a) 2 – 25x2 = 0 => (√2)2 – (5x)2 = 0
=> (√2 – 5x)( √2 + 5x) = 0
Hoặc √2 – 5x = 0 => 5x = √2 => x = √2525
Hoặc √2 + 5x = 0 => 5x = -√2 => x = - √2525
b) x2 - x + 1414 = 0 => x2 – 2 . x . 1212 + (1212)2 = 0
=> (x - 1212)2 = 0 => x - 1212 = 0 => x = 12
10 tháng 8 2018
a) \(x^4+x^2-2=0\)
\(\Leftrightarrow x^4+2x^2-x^2-2=0\)
\(\Leftrightarrow x^2\left(x^2+2\right)-\left(x^2+2\right)=0\)
\(\Leftrightarrow\left(x^2+2\right)\left(x^2-1\right)=0\)
\(\Leftrightarrow\left(x^2+2\right)\left(x+1\right)\left(x-1\right)=0\)
\(\Leftrightarrow x^2+2=0\) hoặc \(x+1=0\) hoặc \(x-1=0\)
. \(x^2+2=0\Leftrightarrow x^2=-2\) (vô nghiệm)
.. \(x+1=0\Leftrightarrow x=-1\)
... \(x-1=0\Leftrightarrow x=1\)
Vậy \(S=\left\{\pm1\right\}\)
b) \(x^4-13x^2+36=0\)
\(\Leftrightarrow x^4-9x^2-4x^2+36=0\)
\(\Leftrightarrow x^2\left(x^2-9\right)-4\left(x^2-9\right)=0
\)
\(\Leftrightarrow\left(x^2-9\right)\left(x^2-4\right)=0\)
\(\Leftrightarrow\left(x+3\right)\left(x-3\right)\left(x+2\right)\left(x-2\right)=0\)
\(\Leftrightarrow x+3=0\) hoặc \(x-3=0\) hoặc \(x+2=0\) hoặc \(x-2=0\)
. \(x+3=0\Leftrightarrow x=-3\)
.. \(x-3=0\Leftrightarrow x=3\)
... \(x+2=0\Leftrightarrow x=-2\)
.... \(x-2=0\Leftrightarrow x=2\)
Vậy \(S=\left\{\pm3;\pm2\right\}\)
Câu C bạn ghi ko rõ lém!!!!!!!!
15 tháng 7 2018
a) \(4.\left(x-1\right)^2-9=0\)
\(\Rightarrow4.\left(x-1\right)^2=9\)
\(\Rightarrow\left(x-1\right)^2=9:4=\dfrac{9}{4}=\left(\pm\dfrac{3}{2}\right)^2\)
\(\Rightarrow x-1=\pm\dfrac{3}{2}\)
\(\Rightarrow\left[{}\begin{matrix}x-1=\dfrac{3}{2}\\x-1=\dfrac{-3}{2}\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{5}{2}\\x=\dfrac{-1}{2}\end{matrix}\right.\)
vậy\(\left[{}\begin{matrix}x=\dfrac{5}{2}\\x=\dfrac{-1}{2}\end{matrix}\right.\)
b) \(\dfrac{1}{4}-9.\left(x-1\right)^2=0\)
\(\Rightarrow9.\left(x-1\right)^2=\dfrac{1}{4}\)
\(\Rightarrow\left(x-1^2\right)=\dfrac{1}{36}=(\pm\dfrac{1}{6})^2\)
\(\Rightarrow x-1=\pm\dfrac{1}{6}\)
\(\Rightarrow\left[{}\begin{matrix}x-1=\dfrac{1}{6}\\x-1=\dfrac{-1}{6}\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{7}{6}\\x=\dfrac{5}{6}\end{matrix}\right.\)
vậy \(\left[{}\begin{matrix}x=\dfrac{7}{6}\\x=\dfrac{5}{6}\end{matrix}\right.\)
15 tháng 7 2018
e) \(\dfrac{1}{16}-\left(2x+\dfrac{3}{4}\right)^2=0\)
\(\Rightarrow\left(2x+\dfrac{3}{4}\right)^2=\dfrac{1}{16}=\left(\pm\dfrac{1}{4}\right)^2\)
\(\Rightarrow2x+\dfrac{3}{4}=\pm\dfrac{1}{4}\)
\(\Rightarrow\)\(\left[{}\begin{matrix}2x+\dfrac{3}{4}=\dfrac{1}{4}\\2x+\dfrac{3}{4}=\dfrac{-1}{4}\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{-1}{4}\\x=\dfrac{-1}{2}\end{matrix}\right.\)
vậy \(\left[{}\begin{matrix}x=\dfrac{-1}{4}\\x=\dfrac{-1}{2}\end{matrix}\right.\)
DH
18 tháng 9 2017
a)(x+1)(x2+2x)=(x+1)x(x+2)=0
\(=>\left\{{}\begin{matrix}x+1=0=>x=-1\\x=0\\x+2=0=>x=-2\end{matrix}\right.\)
b)x(3x-2)-5(2-3x)=x(3x-2)+5(3x-2)=(3x-2)(x+5)=0
\(=>\left\{{}\begin{matrix}3x-2=0=>x=\dfrac{2}{3}\\x+5=0=>x=-5\end{matrix}\right.\)
c)\(\dfrac{4}{9}-25x^2=\left(\dfrac{2}{3}\right)^2-\left(5x\right)^2=\left(\dfrac{2}{3}-5x\right)\left(\dfrac{2}{3}+5x\right)\)
=0
\(=>\left\{{}\begin{matrix}\dfrac{2}{3}-5x=0=>x=\dfrac{2}{15}\\\dfrac{2}{3}+5x=0=>x=\dfrac{-2}{15}\end{matrix}\right.\)
d)\(x^2-x+\dfrac{1}{4}=x^2-2.\dfrac{1}{2}.x+\left(\dfrac{1}{2}\right)^2=\left(x-\dfrac{1}{2}\right)^2=0\)
\(=>x-\dfrac{1}{2}=0=>x=\dfrac{1}{2}\)
13 tháng 9 2018
a) \(x^2-16=0\Rightarrow x^2=16\Rightarrow x^2=\pm4\)
b) \(4x^2-9=0\Rightarrow\left(2x-3\right)\left(2x+3\right)=0\Rightarrow x=\pm1,5\)
c) \(25x^2-1=0\Rightarrow\left(5x-1\right)\left(5x+1\right)=0\Rightarrow x=\pm0,2\)
d) \(4\left(x-1\right)^2-9=0\Rightarrow\left(2x-2-3\right)\left(2x-2+3\right)=0\Rightarrow\left[{}\begin{matrix}2x-5=0\Rightarrow x=2,5\\2x+1=0\Rightarrow x=-0,5\end{matrix}\right.\)
e) \(25x^2-\left(5x+1\right)^2=0\Rightarrow\left(5x+5x+1\right)\left(5x-5x-1\right)=0\Rightarrow10x+1=0\Rightarrow x=-0,1\)
f) \(\dfrac{1}{4}-9\left(x-1\right)^2=0\Rightarrow\left(\dfrac{1}{2}+3x-3\right)\left(\dfrac{1}{2}-3x+3\right)=0\Rightarrow\left[{}\begin{matrix}x=\dfrac{5}{6}\\x=\dfrac{7}{6}\end{matrix}\right.\)
g) \(\dfrac{1}{16}-\left(2x+\dfrac{3}{4}\right)^2=0\Rightarrow\left(\dfrac{1}{4}+2x+\dfrac{3}{4}\right)\left(\dfrac{1}{4}-2x-\dfrac{3}{4}\right)=0\Rightarrow\left[{}\begin{matrix}x=-0,5\\x=-0,25\end{matrix}\right.\)
h) \(\dfrac{1}{9}x^2-\dfrac{2}{3}x+1=0\Rightarrow\left(\dfrac{1}{3}x-1\right)^2=0\Rightarrow\dfrac{1}{3}x=1\Rightarrow x=3\)
k) \(4\left(x-3\right)^2-\left(2-3x\right)^2=0\Rightarrow\left(2x-6+2-3x\right)\left(2x-6-2+3x\right)=0\Rightarrow\left[{}\begin{matrix}-x-4=0\Rightarrow x=-4\\5x-8=0\Rightarrow x=1,6\end{matrix}\right.\)
l) \(x^2-x-12=0\Rightarrow x^2-4x+3x-12=0\Rightarrow x\left(x-4\right)+3\left(x-4\right)=0\Rightarrow\left(x+3\right)\left(x-4\right)=0\Rightarrow\left[{}\begin{matrix}x=-3\\x=4\end{matrix}\right.\)
MT
2
B
18 tháng 9 2020
Bài làm :
\(a\text{)}3x^2+4x=0\Leftrightarrow x\left(3x+4\right)=0\Leftrightarrow\orbr{\begin{cases}x=0\\3x+4=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=0\\x=-\frac{4}{3}\end{cases}}\)
\(b\text{)}25x^2-0,64=0\Leftrightarrow\left(5x-0,8\right)\left(5x+0,8\right)=0\Leftrightarrow\orbr{\begin{cases}5x-0,8=0\\5x+0,8=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=0,16\\-0,16\end{cases}}\)
\(c\text{)}x^4-16x^2=0\Leftrightarrow\left(x^2-4x\right)\left(x^2+4x\right)=0\Leftrightarrow\orbr{\begin{cases}x^2-4x=0\\x^2+4x=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x\left(x-4\right)=0\\x\left(x+4\right)=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=0\\x=\pm4\end{cases}}\)
\(d\text{)}x^2+x=6\Leftrightarrow x^2+x-6=0\Leftrightarrow\left(x^2-2x\right)+\left(3x-6\right)=0\Leftrightarrow x\left(x-2\right)+3\left(x-2\right)=0\Leftrightarrow\left(x+3\right)\left(x-2\right)=0\Leftrightarrow\orbr{\begin{cases}x+3=0\\x-2=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=-3\\x=2\end{cases}}\)
18 tháng 9 2020
Bài làm :
\(a)3x^2+4x=0\)
\(\Rightarrow x\left(3x+4\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x=0\\3x+4=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=0\\x=\frac{-4}{3}\end{cases}}\)
Vậy x = 0 hoặc \(x=\frac{-4}{3}\) .
\(b)25x^2-0,64=0\)
\(\Rightarrow\left(5x\right)^2=\frac{16}{25}\)
\(\Rightarrow\left(5x\right)^2=\left(\frac{4}{5}\right)^2\)
\(\Rightarrow\orbr{\begin{cases}5x=\frac{4}{5}\\5x=\frac{-4}{5}\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{4}{25}\\x=\frac{-4}{25}\end{cases}}\)
Vậy \(x=\frac{4}{25}\) hoặc \(x=\frac{-4}{25}\) .
\(c)x^4-16x^2=0\)
\(\Rightarrow x^2\left(x^2-16\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x^2=0\\x^2-16=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=0\\x^2=4^2\end{cases}}\Rightarrow\orbr{\begin{cases}x=0\\x=\pm4\end{cases}}\)
Vậy x = 0 hoặc \(x=\pm4\) .
12 tháng 2 2017
Bài 2:đk x khác -1 đặt luôn x+1=y y khác 0
\(\Leftrightarrow k\left(y+1\right)-3k+3=y\Leftrightarrow\left(k-1\right)y-2k+3=0\) (*)
với k=1 => 0.y-2+3=1=0 vô nghiệm
với k khác 1 ta có \(y=\frac{2k-3}{k-1}\)
Đk x<0=> y<1
\(\frac{2k-3}{k-1}< 1\Leftrightarrow\frac{2k-3-k+1}{k-1}=\frac{k-2}{k-1}< 0\Rightarrow1< k< 2\)
Bài 3: ĐK x khác -1
\(4-t=\frac{2}{x+1}\Leftrightarrow\left(4-t\right)\left(x+1\right)=2\) (*)
Với t=4 có 0.(x+1)=2 => vô nghiệm
với t khác 4 => (x+1)=2/(4-t)=> x=2/(4-t)-1
nghiệm dương => \(\frac{2}{4-t}-1>0\Rightarrow\frac{2+t-4}{4-t}=\frac{t-2}{4-t}>0\Rightarrow2< t< 4\)
12 tháng 2 2017
Bổ xung: với bài này không ảnh hửng đến đáp số
Bài 2: cần giải thêm
\(\frac{2k-3}{k-1}\ne0\Rightarrow k\ne\frac{3}{2}\)
Bài 3 giải thêm
\(\frac{t-2}{4-t}\ne-1\)
\(a,x^3-13x=0\)
\(x.\left(x^2-13\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x=0\\x^2=13\end{cases}\Rightarrow\orbr{\begin{cases}x=0\\x=\sqrt{13}\end{cases}}}\)
\(b,2-25x^2=0\)
\(\Rightarrow25x^2=2\Rightarrow x^2=\frac{2}{25}\Rightarrow x=\sqrt{\frac{2}{25}}\)
\(c,x^2-x+\frac{1}{4}=0\)
\(\left(x-\frac{1}{2}\right)^2=0\Rightarrow x=\frac{1}{2}\)
a, x 3 - 13 x = 0
=> x ( x 2 - 13 ) = 0
=> \(\orbr{\begin{cases}x=0\\x^2=13\end{cases}\Rightarrow[\begin{cases}x=0\\x=\sqrt{13}\\x=-\sqrt{13}\end{cases}}\)
b, 2 - 25 x 2 = 0
=> 25 x 2 = 2
=> x 2 = 0,08
=> \(\orbr{\begin{cases}x=\frac{\sqrt{2}}{5}\\x=\frac{-\sqrt{2}}{5}\end{cases}}\)
x, x 2 - x + \(\frac{1}{4}\)= 0
=> \(\left(x-\frac{1}{2}\right)^2=0\)
=> \(x-\frac{1}{2}=0\)
=> \(x=\frac{1}{2}\)