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A = ((20 + 1) . 20 : 2) . 2 = 420
B = (25 + 20) . 6 : 2 = 135
C = ( 33 + 26) . 8 : 2 = 236
D = (1 + 100) .100 : 2 = 5050
a.
ĐKXĐ: $x\geq 0$
PT $\Leftrightarrow 6\sqrt{2x}-4\sqrt{2x}+5\sqrt{2x}=21$
$\Leftrightarrow 7\sqrt{2x}=21$
$\Leftrightarrow \sqrt{2x}=3$
$\Leftrightarrow 2x=9$
$\Leftrightarrow x=\frac{9}{2}$ (tm)
b.
ĐKXĐ: $x\geq -2$
PT $\Leftrightarrow \sqrt{25(x+2)}+3\sqrt{4(x+2)}-2\sqrt{16(x+2)}=15$
$\Leftrightarrow 5\sqrt{x+2}+6\sqrt{x+2}-8\sqrt{x+2}=15$
$\Leftrightarrow 3\sqrt{x+2}=15$
$\Leftrightarrow \sqrt{x+2}=5$
$\Leftrightarrow x+2=25$
$\Leftrightarrow x=23$ (tm)
c.
$\sqrt{(x-2)^2}=12$
$\Leftrightarrow |x-2|=12$
$\Leftrightarrow x-2=12$ hoặc $x-2=-12$
$\Leftrightarrow x=14$ hoặc $x=-10$
e.
PT $\Leftrightarrow |2x-1|-x=3$
Nếu $x\geq \frac{1}{2}$ thì $2x-1-x=3$
$\Leftrightarrow x=4$ (tm)
Nếu $x< \frac{1}{2}$ thì $1-2x-x=3$
$\Leftrightarrow x=\frac{-2}{3}$ (tm)
a, \(2\left(x+3\right)\left(x-4\right)=\left(2x-1\right)\left(x+2\right)-27\)
\(\Leftrightarrow2\left(x^2-4x+3x-12\right)=2x^2+4x-x-2-27\)
\(\Leftrightarrow2x^2-2x-24=2x^2+3x-29\Leftrightarrow-5x+5=0\Leftrightarrow x=1\)
b, \(\left(x+2\right)\left(x^2-2x+4\right)-x\left(x-3\right)\left(x+3\right)=26\)
\(\Leftrightarrow x^3-8-x\left(x^2-9\right)=26\Leftrightarrow-8+9x=26\)
\(\Leftrightarrow9x=18\Leftrightarrow x=2\)
a/ \(\left(x-2\right)^2=11+6\sqrt{2}\)
\(\Leftrightarrow\left(x-2\right)^2=\left(3+\sqrt{2}\right)^2\)
\(\Leftrightarrow\left[{}\begin{matrix}x-2=3+\sqrt{2}\\x-2=-3-\sqrt{2}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=5+\sqrt{2}\\x=-1-\sqrt{2}\end{matrix}\right.\)
b/ \(x^2-10x+25=27-10\sqrt{2}\)
\(\Leftrightarrow\left(x-5\right)^2=\left(5-\sqrt{2}\right)^2\)
\(\Leftrightarrow\left[{}\begin{matrix}x-5=5-\sqrt{2}\\x-5=\sqrt{2}-5\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=10-\sqrt{2}\\x=\sqrt{2}\end{matrix}\right.\)
c/ \(4x^2+4x+1=28-10\sqrt{3}\)
\(\Leftrightarrow\left(2x+1\right)^2=\left(5-\sqrt{3}\right)^2\)
\(\Leftrightarrow\left[{}\begin{matrix}2x+1=5-\sqrt{3}\\2x+1=\sqrt{3}-5\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\frac{4-\sqrt{3}}{2}\\x=\frac{-6+\sqrt{3}}{2}\end{matrix}\right.\)
d/ \(x^2+2\sqrt{5}x+5=21-4\sqrt{5}\)
\(\Leftrightarrow\left(x+\sqrt{5}\right)^2=\left(2\sqrt{5}-1\right)^2\)
\(\Leftrightarrow\left[{}\begin{matrix}x+\sqrt{5}=2\sqrt{5}-1\\x+\sqrt{5}=1-2\sqrt{5}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\sqrt{5}-1\\x=1-3\sqrt{5}\end{matrix}\right.\)
e/ \(x^2+2\sqrt{12}x+12=13-4\sqrt{3}\)
\(\Leftrightarrow\left(x+2\sqrt{3}\right)^2=\left(2\sqrt{3}-1\right)^2\)
\(\Leftrightarrow\left[{}\begin{matrix}x+2\sqrt{3}=2\sqrt{3}-1\\x+2\sqrt{3}=1-2\sqrt{3}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-1\\x=1-4\sqrt{3}\end{matrix}\right.\)
f/ \(4x^2-12\sqrt{2}x+18=51-10\sqrt{2}\)
\(\Leftrightarrow\left(2x-3\sqrt{2}\right)^2=\left(5\sqrt{2}-1\right)^2\)
\(\Leftrightarrow\left[{}\begin{matrix}2x-5\sqrt{2}=5\sqrt{2}-1\\2x-2\sqrt{2}=1-5\sqrt{2}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\frac{10\sqrt{2}-1}{2}\\x=\frac{1-3\sqrt{2}}{2}\end{matrix}\right.\)
c) \(\sqrt{\left(x-2\right)^2}=10\)
\(x-2=10\)
\(x=12\)
d) \(\sqrt{9x^2-6x+1}=15\)
\(\sqrt{\left(3x\right)^2-2.3x.1+1^2}=15\)
\(\sqrt{\left(3x-1\right)^2}=15\)
\(3x-1=15\)
\(3x=16\)
\(x=\dfrac{16}{3}\)
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) \(đk:x\ge\dfrac{8}{3}\)
\(pt\Leftrightarrow3x+4=9x^2-48x+64\)
\(\Leftrightarrow9x^2-51x+60=0\)
\(\Leftrightarrow3\left(x-4\right)\left(5x-3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=4\left(tm\right)\\x=\dfrac{5}{3}\left(ktm\right)\end{matrix}\right.\)
a) 12 . ( x - 1 ) = 0
x - 1 = 0 : 12
x - 1 = 0
x = 0 + 1
x = 1
b) ( 6x - 39 ) : 3 = 201
6x - 39 = 201 . 3
6x - 39 = 603
6x = 603 + 39
6x = 642
x = 642 : 6
x = 107
c) 23 + 3x = 56 : 53
23 + 3x = 53
23 + 3x = 125
3x = 125 - 23
3x = 102
x = 102 : 3
x = 34
Các phần d , e , f Đỗ Ngọc Hoàng Hải làm tương tự như phần trên .
a/x =1 nha
b/(6x-39):3=201
6x-39 =201x3
6x-39 =603
6x = 603+39
6x = 642
6= 642:6=107
c/ 23+3.x=125
3x= 125-23=102
x= 102:3=34
d/ 541+(281-x)=735
281-x= 735-541=194
x=281-194=87
e/ 9x+2=20
9x=20-2
9x=18
x=18:9=9
f/71+(26-3x):5=75
(26-3x):5=75-71=4
26-3x=4x5=20
3x=26-20=6
x=6:3=2
tk nha ^^
f) Ta có: \(\sqrt{16\left(x+1\right)}-\sqrt{9\left(x+1\right)}=4\)
\(\Leftrightarrow4\left|x+1\right|-3\left|x+1\right|=4\)
\(\Leftrightarrow\left|x+1\right|=4\)
\(\Leftrightarrow\left[{}\begin{matrix}x+1=4\\x+1=-4\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-5\end{matrix}\right.\)
g) Ta có: \(\sqrt{9x+9}+\sqrt{4x+4}=\sqrt{x+1}\)
\(\Leftrightarrow5\sqrt{x+1}-\sqrt{x+1}=0\)
\(\Leftrightarrow x+1=0\)
hay x=-1
a, \(A=\sqrt{8}-2\sqrt{15}-\sqrt{8}+2\sqrt{15}\)
\(=\left(\sqrt{8}-\sqrt{8}\right)+\left(-2\sqrt{15}+2\sqrt{15}\right)=0\)
b, \(B=\sqrt{49}+20\sqrt{6}+\sqrt{49}-20\sqrt{6}\)
\(=\left(\sqrt{49}+\sqrt{49}\right)+\left(20\sqrt{6}-20\sqrt{6}\right)=14\)
c, Không rõ đề
d, Không rõ đề
-Viết đề chán v!
a: =>|x-2|+|x-3|=1
TH1: x<2
Pt sẽ là 2-x+3-x=1
=>5-2x=1
=>x=2(loại)
TH2: 2<=x<3
Pt sẽ là x-2+3-x=1
=>1=1(nhận)
TH3: x>=3
Pt sẽ là x-2+x-3=1
=>2x=6
=>x=3(nhận)
b: ĐKXĐ: x>=-2
\(\Leftrightarrow\left|\sqrt{x+2}-2\right|+\left|\sqrt{x+2}-3\right|=1\)
TH1: \(\sqrt{x+2}< 2\Leftrightarrow0< =x+2< 4\Leftrightarrow-2< =x< 2\)
Pt sẽ là \(2-\sqrt{x+2}+3-\sqrt{x+2}=1\)
=>5-2 căn x+2=1
=>2 căn x+2=4
=>x+2=4
=>x=2(loại)
TH2: 2<=căn x+2<3
=>4<=x+2<9
=>2<=x<7
Pt sẽ là \(\sqrt{x+2}-2+3-\sqrt{x+2}=1\)
=>1=1(nhận)
TH3: căn x+2>=3
=>x+2>=9
=>x>=7
Pt sẽ là \(\sqrt{x+2}-3+\sqrt{x+2}-2=1\)
=>2 căn x+2=6
=>x+2=9
=>x=7(nhận)
a, 720 : ( x - 17 ) = 12
=> x - 17 = 720 : 12 = 60
=> x = 60 + 17 = 77
\(a,\text{ }720\text{ : }\left(x-17\right)=12\)
\(\left(x-17\right)=720\text{ : }12\)
\(\left(x-17\right)=60\)
\(x=60+17\)
\(x=77\)
b, 26 + 8x = 6x + 46
=> 8x - 6x = 46 - 26
=> 2x = 20
=>x = 20: 2 =10
\(b,\text{ }26+8x=6x+46\)
\(\Rightarrow\text{ }2x=46-26\)
\(2x=20\)
\(x=20\text{ : }2\)
\(x=10\)
\(c,\text{ }\left(x-28\right)\text{ : }12=8\)
\(\left(x-28\right)=8\text{ x }12\)
\(\left(x-28\right)=96\)
\(x=96+28\)
\(x=124\)
\(d,\text{ }3\left(x-6\right)-11=22\)
\(3\left(x-6\right)=22+11\)
\(3\left(x-6\right)=33\)
\(\left(x-6\right)=33\text{ : }3\)
\(\left(x-6\right)=11\)
\(x=11+6\)
\(x=17\)
a) 77
b) 10
c) 124
d) 17
e) 5
f) 10
chúc bạn học tốt
c, ( x - 28 ) : 12 = 8
=> x - 28 = 8 x 12 = 96
=> x = 96 + 28 = 124
3 ( x - 6 ) - 11 = 22
=> 3(x - 6 ) = 22+11=33
=> x - 6 = 33:3=11
=> x = 11+6=17
e, 5 ( x + 2 ) + 8 = 23
=> 5 ( x + 2 ) = 23 - 8 = 15
=> x + 2 = 15 : 5 = 3
=>x = 3 -2 =1
f, 4x - 15 - 5 = 20
=> 4x = 20 + 15 + 5
=> 4x = 20
=> x = 20 :4 = 5
a) \(720:\left(x-17\right)=12\)
\(\Leftrightarrow\) \(x-17=60\)
\(\Leftrightarrow\) \(x=77\)
Vậy......
b) \(26+8x=6x+46\)
\(\Leftrightarrow\)\(8x-6x=46-26\)
\(\Leftrightarrow\) \(2x=20\)
\(\Leftrightarrow\) \(x=10\)
Vậy.............
c) \(\left(x-28\right):12=8\)
\(\Leftrightarrow\) \(x-28=96\)
\(\Leftrightarrow\) \(x=124\)
Vậy..........
d) \(3\left(x-6\right)-11=22\)
\(\Leftrightarrow\) \(3\left(x-6\right)=33\)
\(\Leftrightarrow\) \(x-6=11\)
\(\Leftrightarrow\) \(x=17\)
Vậy........
e) \(5\left(x+2\right)+8=23\)
\(\Leftrightarrow\) \(5\left(x+2\right)=15\)
\(\Leftrightarrow\) \(x+2=3\)
\(\Leftrightarrow\) \(x=1\)
f) \(4x-15-5=20\)
\(\Leftrightarrow\) \(4x-20=20\)
\(\Leftrightarrow\) \(4x=40\)
\(\Leftrightarrow\) \(x=10\)
Vậy.....
\(a,720:\left(x-17\right)=12\)
\(\Rightarrow x-17=720:12=60\)
\(\Rightarrow x=60+17=77\)
\(b,26+8x=6x+46\)
\(\Rightarrow8x-6x=46-26\)
\(\Rightarrow2x=20\)
\(\Rightarrow x=20:2=10\)
\(c,\left(x-28\right):12=8\)
\(\Rightarrow x-28=8.12=96\)
\(\Rightarrow x=96+28=124\)
\(d,3\left(x-6\right)-11=22\)
\(\Rightarrow3\left(x-6\right)=22+11=33\)
\(\Rightarrow x-6=33:3=11\)
\(\Rightarrow x=11+6=17\)
\(e,5\left(x+2\right)+8=23\)
\(\Rightarrow5\left(x+2\right)=23-8=15\)
\(\Rightarrow x+2=15:5=3\)
\(\Rightarrow x=3-2=1\)
\(f,4x-15-5=20\)
\(\Rightarrow4x=20+15+5=40\)
\(\Rightarrow x=40:4=10\)