Tìm x,y biết:
a, (3x-5)(\(\frac{3}{2}\)x+2)(0,5x-10)=0
b, |x-\(\frac{1}{3}\)|+|x-y|=0
(Mn giúp mik vs T-T)
K
Khách
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8 tháng 9 2016
a) \(\left|2x\right|-\left|-2,5\right|=\left|-7,5\right|\)
\(\Leftrightarrow\left|2x\right|-2,5=7,5\)
\(\Leftrightarrow\left|2x\right|=10\)
\(\Leftrightarrow\begin{cases}x\ge0\\2x=10\end{cases}\) hoặc \(\begin{cases}x< 0\\2x=-10\end{cases}\)
\(\Leftrightarrow\begin{cases}x\ge0\\x=5\left(tm\right)\end{cases}\) hoặc \(\begin{cases}x< 0\\x=-5\left(tm\right)\end{cases}\)
Vậy x={5;-5}
b)\(\left|3x\right|\cdot\left|-3,5\right|=\left|-2,8\right|\)
\(\Leftrightarrow\left|3x\right|\cdot3,5=2,8\)
\(\Leftrightarrow\left|3x\right|=\frac{4}{5}\)
\(\Leftrightarrow\begin{cases}x\ge0\\3x=\frac{4}{5}\end{cases}\) hoặc \(\begin{cases}x< 0\\3x=-\frac{4}{5}\end{cases}\)
\(\Leftrightarrow\begin{cases}x\ge0\\x=\frac{4}{15}\end{cases}\) hoặc \(\begin{cases}x< 0\\x=-\frac{4}{15}\end{cases}\)
Vậy x={4/15;-4/15}
c) \(\left(3x-5\right)\left(\frac{3}{2}x+2\right)\left(0,5x-10\right)=0\)
\(\Leftrightarrow\left[\begin{array}{nghiempt}3x-5=0\\\frac{3}{2}x+2=0\\0,5x-10=0\end{array}\right.\)\(\Leftrightarrow\left[\begin{array}{nghiempt}x=\frac{5}{3}\\x=-\frac{4}{3}\\x=20\end{array}\right.\)
EC
8 tháng 9 2016
a)|2x|-|-2,5|=|-7,5|
|2x|-2,5=7,5
|2x|=10
\(\Rightarrow\left[\begin{array}{nghiempt}2x=10\\2x=-10\end{array}\right.\)\(\Rightarrow\left[\begin{array}{nghiempt}x=5\\x=-5\end{array}\right.\)
Vậy x=5;-5
30 tháng 1 2020
b) \(\left|5x-3\right|-x=7\)
\(\Rightarrow\left|5x-3\right|=7+x\)
\(\Rightarrow\orbr{\begin{cases}5x-3=7+x\\5x-3=-\left(7+x\right)\end{cases}\Rightarrow\orbr{\begin{cases}5x-3=7+x\\5x-3=-7-x\end{cases}\Rightarrow}\orbr{\begin{cases}5x-x=7+3\\5x+x=-7+3\end{cases}}}\)
\(\Rightarrow\orbr{\begin{cases}4x=10\\6x=-4\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{5}{2}\\x=-\frac{2}{3}\end{cases}}}\)
Vậy ....................
30 tháng 1 2020
Bạn ơi !!! ý A tham khảo tại link này nè :
https://h.vn/hoi-dap/question/394208.html
~ Học tốt ~
H
16 tháng 3 2023
\(\dfrac{x-1}{x}-\dfrac{1}{x+1}=\dfrac{2x-1}{x^2+x}\)
\(\Leftrightarrow\dfrac{x-1}{x}-\dfrac{1}{x+1}=\dfrac{2x-1}{x\left(x+1\right)}\)
ĐKXĐ : \(\left\{{}\begin{matrix}x\ne0\\x+1\ne0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x\ne0\\x\ne-1\end{matrix}\right.\)
Ta có : `(x-1)/x -1/(x+1) =(2x-1)/(x(x+1))`
\(\Leftrightarrow\dfrac{\left(x-1\right)\left(x+1\right)}{x\left(x+1\right)}-\dfrac{x}{x\left(x+1\right)}=\dfrac{2x-1}{x\left(x+1\right)}\)
`=> x^2 +x -x-1 -x-2x+1=0`
`<=> x^2 -3x =0`
`<=> x(x-3)=0`
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x-3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\left(ktm\right)\\x=3\end{matrix}\right.\)
__
`(x+2)(5-3x)=0`
\(\Leftrightarrow\left[{}\begin{matrix}x+2=0\\5-3x=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-2\\3x=5\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=\dfrac{5}{3}\end{matrix}\right.\)
__
\(\dfrac{5\left(1-2x\right)}{3}+\dfrac{x}{2}=\dfrac{3\left(x-5\right)}{4}-2\)
\(\Leftrightarrow\dfrac{20\left(1-2x\right)}{12}+\dfrac{6x}{12}=\dfrac{9\left(x-5\right)}{12}-\dfrac{24}{12}\)
`<=> 2x- 40x + 6x = 9x - 45 -24`
`<=> 2x- 40x + 6x-9x + 45 +24=0`
`<=>-41x+69=0`
`<=>-41x=-69`
`<=> x=69/41`
16 tháng 3 2023
a:=>x^2-1-x=2x-1
=>x^2-x-1=2x-1
=>x^2-3x=0
=>x=0(loại) hoặc x=3(nhận)
b:=>x+2=0 hoặc 5-3x=0
=>x=-2 hoặc x=5/3
c:=>20(1-2x)+6x=9(x-5)-24
=>20-40x+6x=9x-45-24
=>-34x+20=9x-69
=>-43x=-89
=>x=89/43
d: =>x^2+4x+4-x^2-2x+3=2x^2+8x-4x-16-3
=>2x^2+4x-19=-2x+7
=>2x^2+6x-26=0
=>x^2+3x-13=0
=>\(x=\dfrac{-3\pm\sqrt{61}}{2}\)
e: =>(2x-3)(2x-3-x-1)=0
=>(2x-3)(x-4)=0
=>x=4 hoặc x=3/2
Y
1 tháng 8 2018
Bài 1:
a) \(8\left(x-2\right)-2\left(3x-4\right)=2\)
\(\Rightarrow2\left[4\left(x-2\right)-\left(3x-4\right)\right]=2\)
\(\Rightarrow4\left(x-2\right)-3x+4=0\)
\(\Rightarrow4x-8-3x+4=0\)
\(\Rightarrow x-4=0\)
\(\Rightarrow x=4\)
b) \(10\left(3x-2\right)-3\left(5x+2\right)+5\left(11-4x\right)=25\)
\(\Rightarrow5\left[2\left(3x-2\right)+11-4x\right]-3\left(5x+2\right)=25\)
\(\Rightarrow5\left(6x-4+11-4x\right)-3\left(5x+2\right)=25\)
\(\Rightarrow5\left(2x+7\right)-3\left(5x+2\right)=25\)
\(\Rightarrow10x+35-15x-6=25\)
\(\Rightarrow-5x+29=25\)
\(\Rightarrow-5x=25-29\)
\(\Rightarrow-5x=-4\)
\(\Rightarrow x=\dfrac{4}{5}\)
c) \(2x\left(x+1\right)-x^2\left(x+2\right)+x^3-x+4=0\)
\(\Rightarrow2x^2+2x-x^3-2x^2+x^3-x+4=0\)
\(\Rightarrow x+4=0\)
\(\Rightarrow x=-4\)
d) \(4x\left(3x+2\right)-6x\left(2x+5\right)+21\left(x-1\right)=0\)
\(\Rightarrow12x^2+8x-12x^2-30x+21x-21=0\)
\(\Rightarrow-x-21=0\)
\(\Rightarrow x=-21\)
Bài 2:
a) \(P=\left(4x^2-3y\right)2y-\left(3x^2-4y\right)3y\)
\(P=8x^2y-6y^2-9x^2y+12y^2\)
\(P=-x^2y+6y^2\)
Thay x = -1 ; y = 2 vào P ta được
\(P=-\left(-1\right)^2.2+6.2^2\)
\(P=-2+24=22\)
b) \(Q=4x^2\left(5x-3y\right)-x^2\left(4x+y\right)\)
\(Q=20x^3-12x^2y-4x^3-x^2y\)
\(Q=16x^3-13x^2y\)
Thay x = -1 ; y = 2 vào Q ta được
\(Q=16\left(-1\right)^3-13\left(-1\right)^2.2\)
\(Q=-16-26\)
\(Q=-42\)
c) \(H=x\left(x^3-y\right)+x^2\left(y-x^2\right)-y\left(x^2-3x\right)\)
\(H=x^4-xy+x^2y-x^4-x^2y+3xy\)
\(H=2xy\)
Thay x = 1/4 ; y = 2012 vào H ta được
\(H=2.\dfrac{1}{4}.2012\)
\(H=1006\)
T
1 tháng 8 2018
1.a)\(8\left(x-2\right)-2\left(3x-4\right)=2\)
\(\Leftrightarrow8x-16-6x+8=2\)
\(\Leftrightarrow2x-8=2\Leftrightarrow2x=10\Leftrightarrow x=5\)
b)\(10\left(3x-2\right)-3\left(5x+2\right)+5\left(11-4x\right)=25\)
\(\Leftrightarrow30x-20-15x-6+55-20x=25\)
\(\Leftrightarrow-5x+29=25\Leftrightarrow-5x=-4\Leftrightarrow x=\dfrac{4}{5}=0,8\)
\(c)2x\left(x+1\right)-x^2\left(x+2\right)+x^3-x+4=0\)
\(\Leftrightarrow2x^2+2x-x^3-2x^2+x^3-x+4=0\)
\(\Leftrightarrow x+4=0\Leftrightarrow x=-4\)
\(d)4x\left(3x+2\right)-6x\left(2x+5\right)+21\left(x-1\right)=0\)
\(\Leftrightarrow12x^2+8x-12x^2-30x+21x-21=0\)
\(\Leftrightarrow-x-21=0\Leftrightarrow-x=21\Leftrightarrow x=-21\)
2.
a)\(P=\left(4x^2-3y\right)2y-\left(3x^2-4y\right)3y\)
\(\Leftrightarrow8x^2y-6y^2-9x^2y-12y^2\)
\(\Leftrightarrow x^2y-18y^2\)
tại x=-1 , y=2
ta có:\(x^2y-18y^2=\left(-1\right)^2.2-18.2^2=2-72=-70\)
vậy \(P=\left(4x^2-3y\right)2y-\left(3x^2-4y\right)3y=-70\) tại x=-1,y=2
b)\(Q=4x^2\left(5x-3y\right)-x^2\left(4x+y\right)\)
\(\Leftrightarrow20x^3-12x^2y-4x^3-x^2y\)
\(\Leftrightarrow17x^3-13x^2y\)
tại x=-1,y=2
ta có:\(17x^3-13x^2y=17\left(-1\right)^3-13\left(-1\right)^2.2=-17-26=-43\)
vậy \(Q=4x^2\left(5x-3y\right)-x^2\left(4x+y\right)=-43\)
c)\(H=x\left(x^3-y\right)+x^2\left(y-x^2\right)-y\left(x^2-3x\right)\)
\(\Leftrightarrow x^4-xy+x^2y-x^3-x^2y+3xy\)
\(\Leftrightarrow x^4+2xy-x^3\)
tại x=1/4 và y=2012
ta có:\(x^4+2xy-x^3=\left(\dfrac{1}{4}\right)^4+2.\dfrac{1}{4}.2012-\left(\dfrac{1}{4}\right)^3\approx1006\)
XO
24 tháng 6 2021
Ta có : \(\hept{\begin{cases}\left|5-\frac{2}{3}x\right|\ge0\forall x\\\left|\frac{1}{7}y-3\right|\ge0\forall y\end{cases}}\Leftrightarrow\left|5-\frac{2}{3}x\right|+\left|\frac{1}{7}y-3\right|\ge0\forall x;y\)
Dấu "=" xảy ra <=> \(\hept{\begin{cases}5-\frac{2}{3}x=0\\\frac{1}{7}y-3=0\end{cases}}\Leftrightarrow\hept{\begin{cases}x=\frac{15}{2}\\y=21\end{cases}}\)
b) Ta có \(\hept{\begin{cases}\left|5x+10\right|\ge0\forall x\\\left|6y-9\right|\ge0\forall y\end{cases}}\Leftrightarrow\left|5x+10\right|+\left|6y-9\right|\ge0\forall x;y\)
Dấu "=" xảy ra <=> \(\hept{\begin{cases}5x+10=0\\6y-9=0\end{cases}}\Leftrightarrow\hept{\begin{cases}x=-2\\y=1,5\end{cases}}\)
KN
17 tháng 8 2020
a. Vì \(\left|x+\frac{1}{2}\right|\ge0\forall x;\left|y-\frac{3}{4}\right|\ge0\forall y;\left|z-1\right|\ge0\forall z\)
\(\Rightarrow\left|x+\frac{1}{2}\right|+\left|y-\frac{3}{4}\right|+\left|z-1\right|\ge0\forall x;y;z\)
Dấu "=" xảy ra <=> | x + 1/2 | = 0 ; | y - 3/4 | = 0 ; | z - 1 | = 0
<=> x = - 1/2 ; y = 3/4 ; z = 1
b. Vì \(\left|x-\frac{3}{4}\right|\ge0\forall x;\left|\frac{2}{5}-y\right|\ge0\forall y\left|x-y+z\right|\ge0\forall x;y;z\)
\(\Rightarrow\left|x-\frac{3}{4}\right|+\left|\frac{2}{5}-y\right|+\left|x-y+z\right|\ge0\forall x;y;z\)
Dấu "=" xảy ra <=> | x - 3/4 | = 0 ; | 2/5 - y | = 0 ; | x - y + z | = 0
<=> x = 3/4 ; y = 2/5 ; z = - 7/20
XO
17 tháng 8 2020
a) Ta có \(\hept{\begin{cases}\left|x+\frac{1}{2}\right|\ge0\forall x\\\left|y-\frac{3}{4}\right|\ge0\forall y\\\left|z-1\right|\ge0\forall z\end{cases}}\Rightarrow\left|x+\frac{1}{2}\right|+\left|y-\frac{3}{4}\right|+\left|z-1\right|\ge0\forall x;y;z\)
Dấu "=" xảy ra <=> \(\hept{\begin{cases}x+\frac{1}{2}=0\\y-\frac{3}{4}=0\\z-1=0\end{cases}}\Rightarrow\hept{\begin{cases}x=-\frac{1}{2}\\y=\frac{3}{4}\\z=1\end{cases}}\)
Vậy x = -1/2 = y = 3/4 ; z = 1
b) Ta có : \(\hept{\begin{cases}\left|x-\frac{3}{4}\right|\ge0\forall x\\\left|\frac{2}{5}-y\right|\ge0\forall y\\\left|x-y+z\right|\ge0\forall x;y;z\end{cases}}\Rightarrow\left|x-\frac{3}{4}\right|+\left|\frac{2}{5}-y\right|+\left|x-y+z\right|\ge0\forall x;y;z\)
Dấu "=" xảy ra <=> \(\hept{\begin{cases}x-\frac{3}{4}=0\\\frac{2}{5}-y=0\\x-y+z=0\end{cases}}\Rightarrow\hept{\begin{cases}x=\frac{3}{4}\\y=\frac{2}{5}\\\frac{3}{4}-\frac{2}{5}+z=0\end{cases}}\Rightarrow\hept{\begin{cases}x=\frac{3}{4}\\y=\frac{2}{5}\\z=-\frac{7}{20}\end{cases}}\)
Vậy x = 3/4 ; y = 2/5 ; z = -7/20
16 tháng 10 2019
b) \(\left(5x-1\right)\left(2x-\frac{1}{3}\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}5x-1=0\\2x-\frac{1}{3}=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}5x=1\\2x=\frac{1}{3}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\frac{1}{5}\\x=\frac{1}{6}\end{matrix}\right.\)
DH
16 tháng 10 2019
e, \(-\frac{3}{4}-\left|\frac{4}{5}-x\right|=-1\)
\(\Leftrightarrow\left|\frac{4}{5}-x\right|=-\frac{3}{4}-\left(-1\right)\)
\(\Leftrightarrow\left|\frac{4}{5}-x\right|=\frac{1}{4}\)
\(\Leftrightarrow\left[{}\begin{matrix}\frac{4}{5}-x=\frac{1}{4}\\\frac{4}{5}-x=-\frac{1}{4}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\frac{7}{15}\\x=1,05\end{matrix}\right.\)
Vậy ....
a) \(\left(3x-5\right).\left(\frac{3}{2}x+2\right).\left(0,5x-10\right)=0\)
⇒ \(\left\{{}\begin{matrix}3x-5=0\\\frac{3}{2}x+2=0\\0,5x-10=0\end{matrix}\right.\) ⇒ \(\left\{{}\begin{matrix}3x=0+5=5\\\frac{3}{2}x=0-2=-2\\0,5x=0+10=10\end{matrix}\right.\) ⇒ \(\left\{{}\begin{matrix}x=5:3\\x=\left(-2\right):\frac{3}{2}\\x=10:0,5\end{matrix}\right.\)
⇒ \(\left\{{}\begin{matrix}x=\frac{5}{3}\\x=-\frac{4}{3}\\x=20\end{matrix}\right.\)
Vậy \(x\in\left\{\frac{5}{3};-\frac{4}{3};20\right\}.\)
b) \(\left|x-\frac{1}{3}\right|+\left|x-y\right|=0\)
⇒ \(\left\{{}\begin{matrix}x-\frac{1}{3}=0\\x-y=0\end{matrix}\right.\)
+) \(x-\frac{1}{3}=0\)
⇒ \(x=0+\frac{1}{3}\)
⇒ \(x=\frac{1}{3}.\)
+) \(x-y=0\)
⇒ \(\frac{1}{3}-y=0\)
⇒ \(y=\frac{1}{3}-0\)
⇒ \(y=\frac{1}{3}.\)
Vậy \(\left(x;y\right)\in\left\{\frac{1}{3}\right\}.\)
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