26 - 3 . (2x - 3)2 = -72
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MH
4 tháng 10 2021
c) \(\sqrt{\left(x-2\right)^2}=10\)
\(x-2=10\)
\(x=12\)
d) \(\sqrt{9x^2-6x+1}=15\)
\(\sqrt{\left(3x\right)^2-2.3x.1+1^2}=15\)
\(\sqrt{\left(3x-1\right)^2}=15\)
\(3x-1=15\)
\(3x=16\)
\(x=\dfrac{16}{3}\)
4 tháng 10 2021
a) \(đk:x\ge0\)
\(pt\Leftrightarrow3\sqrt{2x}+4\sqrt{2x}-3\sqrt{2x}=12\)
\(\Leftrightarrow4\sqrt{2x}=12\Leftrightarrow\sqrt{2x}=3\Leftrightarrow2x=9\Leftrightarrow x=\dfrac{9}{2}\left(tm\right)\)
b) \(đk:x\ge-2\)
\(pt\Leftrightarrow3\sqrt{x+2}+12\sqrt{x+2}-2\sqrt{x+2}=26\)
\(\Leftrightarrow13\sqrt{x+2}=26\)
\(\Leftrightarrow\sqrt{x+2}=2\Leftrightarrow x+2=4\Leftrightarrow x=2\left(tm\right)\)
c) \(pt\Leftrightarrow\left|x-2\right|=10\)
\(\Leftrightarrow\left[{}\begin{matrix}x-2=10\\x-2=-10\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}x=12\\x=-8\end{matrix}\right.\)
d) \(pt\Leftrightarrow\sqrt{\left(3x-1\right)^2}=15\)
\(\Leftrightarrow\left|3x-1\right|=15\)
\(\Leftrightarrow\left[{}\begin{matrix}3x-1=15\\3x-1=-15\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{16}{3}\\x=-\dfrac{14}{3}\end{matrix}\right.\)
e) \(đk:x\ge\dfrac{8}{3}\)
\(pt\Leftrightarrow3x+4=9x^2-48x+64\)
\(\Leftrightarrow9x^2-51x+60=0\)
\(\Leftrightarrow3\left(x-4\right)\left(5x-3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=4\left(tm\right)\\x=\dfrac{5}{3}\left(ktm\right)\end{matrix}\right.\)
KC
5 tháng 7 2016
a) 12-3x=0
3x=12-0
3x=12
x=12:3
x=4
b)2x-26=25.12
2x-26=300
2x=300+26
2x=326
x=326:2
x=163
c)5x+28=234:3
5x+28=78
5x=78-28
5x=50
x=50:5
x=10
d)72-7x=529:23
72-7x=23
7x=72-23
7x=49
x=49:7
x=7
k cho mình nhoa~~
5 tháng 7 2016
a, (12-3x):20=0
=> 12-3x=0
=> 3x=12
=> x= 4 Vậy x=4
b, (2x-26):12=25
=> 2x-26=300
=> 2x=326
=> x=163 Vậy x= 163
c, 234:( 5x+28)=3
=> 5x+28=78
=> 5x=50
=> x= 10 Vậy x= 10
d, 529: (72-7x)=23
=> 72-7x=23
=> 7x=49
=> x= 7 Vậy x= 7
Nhớ k cho mik nhé!!!! CẢM ƠN !!!
28 tháng 10 2019
a, Đặt \(\frac{x}{4}=\frac{y}{7}=\frac{z}{5}=k\Rightarrow\left\{{}\begin{matrix}x=4k\\y=7k\\z=5k\end{matrix}\right.\)
Mà \(yz-xy-z^2=-72\)
\(\Rightarrow35k^2-28k^2-25k^2=-72\\ \Rightarrow k^2\left(35-28-25\right)=-72\\ k^2\cdot\left(-18\right)=-72\\ \Rightarrow k^2=4\\ \Rightarrow\left[{}\begin{matrix}k=2\\k=-2\end{matrix}\right.\)
Với k = 2
\(\Rightarrow\left\{{}\begin{matrix}x=4\cdot2=8\\y=7\cdot2=14\\z=5\cdot2=10\end{matrix}\right.\)
Với k = -2
\(\Rightarrow\left\{{}\begin{matrix}x=4\cdot\left(-2\right)=-8\\y=7\cdot\left(-2\right)=-14\\z=5\cdot\left(-2\right)=-10\end{matrix}\right.\)
Vậy \(\left(x;y;z\right)\in\left\{\left(8;14;10\right);\left(-8;-14;-10\right)\right\}\)
b, Đặt \(\frac{x}{2}=\frac{y}{7}=\frac{z}{8}=k\Rightarrow\left\{{}\begin{matrix}x=2k\\y=7k\\z=8k\end{matrix}\right.\)
Mà \(2x^2+xy-xz=54\)
\(\Rightarrow8k^2+14k^2-16k^2=54\\ \Rightarrow k^2\left(8+14-16\right)=54\\ \Rightarrow k^2\cdot6=54\\ \Rightarrow k^2=9\\ \Rightarrow\left[{}\begin{matrix}k=3\\k=-3\end{matrix}\right.\)
Với k = 3
\(\Rightarrow\left\{{}\begin{matrix}x=2\cdot3=6\\y=7\cdot3=21\\z=8\cdot3=24\end{matrix}\right.\)
Với k = -3
\(\Rightarrow\left\{{}\begin{matrix}x=2\cdot\left(-3\right)=-6\\y=7\cdot\left(-3\right)=-21\\z=8\cdot\left(-3\right)=-24\end{matrix}\right.\)
Vậy \(\left(x;y;z\right)\in\left\{\left(6;21;24\right);\left(-6;-21;-24\right)\right\}\)
c, Đặt \(\frac{x+3}{5}=\frac{y-4}{3}=\frac{z-5}{2}=k\Rightarrow\left\{{}\begin{matrix}x=5k-3\\y=3k+4\\z=2k+5\end{matrix}\right.\)
Mà \(2x-3y-z=-26\)
\(\Rightarrow2\left(5k-3\right)-3\left(3k+4\right)-\left(2k+5\right)=-26\\ \Rightarrow10k-6-9k-12-2k-5=-26\\ \Rightarrow-k=-3\\ \Rightarrow k=3\\ \Rightarrow\left\{{}\begin{matrix}x=5\cdot3-3=12\\y=3\cdot3+4=13\\z=2\cdot3+5=11\end{matrix}\right.\)
Vậy \(\left(x;y;z\right)=\left(12;13;11\right)\)
H
0
21 tháng 1 2017
Bài 1:
1)-53
2)-200800
3)1230000
Bài 2:
a) x=3
b) x=3
Bài 3:
a)A=-250
b)x=1
L
1
M
29 tháng 1 2020
Bài giải
a, \(-2\left(2x-8\right)+3\left(4-2x\right)=-72-5\left(3x-7\right)\)
\(-4x+8+12-6x=-72-15x+7\)
\(-10x+20=-65-15x\)
\(-10x+15x=-65-20\)
\(5x=-85\)
\(x=-85\text{ : }5\)
\(x=-17\)
b, \(3\left|2x^2-7\right|=33\)
\(\left|2x^2-7\right|=33\text{ : }3\)
\(\left|2x^2-7\right|=11\)
\(\Rightarrow\orbr{\begin{cases}2x^2-7=-11\\2x^2-7=11\end{cases}}\Rightarrow\orbr{\begin{cases}2x^2=-4\text{ ( loại ) }\\2x^2=18\end{cases}}\Rightarrow\text{ }x^2=9\text{ }\Rightarrow\text{ }x=\pm3\)
\(\Rightarrow\text{ }x=\pm3\)
NN
4
24 tháng 2 2021
`1,[(-3).3+5]-26=-2x-3`
`=>(-9+5)-26=-2x-3`
`=>-4-26=-2x-3`
`=>-30=-2x-3`
`=>-2x=-27`
`=>x=27/2`
Vậy `x=27/2`
`2)-[(-35)-3]=2x-2`
`=>-(-38)=2x-2`
`=>38=2x-2`
`=>2x=40`
`=>x=20`
Vậy `x=20`
24 tháng 2 2021
1) \(\left[\left(-3\right)\cdot3+5\right]-26=-2x-3\\ \Rightarrow-9+5-26=-2x-3\\ \Rightarrow-2x=-9+5-26+3\\ \Rightarrow-2x=-27\\ \Rightarrow x=\dfrac{27}{2}\)
Vậy \(x=\dfrac{27}{2}\)
2) \(-\left[\left(-35\right)-3\right]=2x-2\\ \Rightarrow2x-2=-\left(-38\right)\\ \Rightarrow2x=38+2\\ \Rightarrow2x=40\\ \Rightarrow x=20\)
Vậy \(x=20\)
x=29/3=9.667
Bài này toán lớp 7 rồi bạn.