-2.(x+3)-15=3.(4+2x)+7
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NT
0
13 tháng 11 2021
\(1,\Leftrightarrow x^2+10x+25=x^2-4x-21\\ \Leftrightarrow14x=-46\\ \Leftrightarrow x=-\dfrac{23}{7}\\ 2,\Leftrightarrow x^3+8=15+x^3+2x\\ \Leftrightarrow2x=-7\Leftrightarrow x=-\dfrac{7}{2}\\ 3,\Leftrightarrow\left(x+3\right)^2=0\\ \Leftrightarrow x=-3\\ 4,\Leftrightarrow x^3-9x^2+27x-27=0\\ \Leftrightarrow\left(x-3\right)^3=0\\ \Leftrightarrow x-3=0\Leftrightarrow x=3\\ 5,\Leftrightarrow4x^2+4x+1-4x^2-16x-16=9\\ \Leftrightarrow-12x=24\Leftrightarrow x=-2\\ 6,\Leftrightarrow x^2-3x+5x-15=0\\ \Leftrightarrow\left(x-3\right)\left(x+5\right)=0\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-5\end{matrix}\right.\)
27 tháng 2 2023
a: =2/5-3/5+3/7=3/7-1/5
=15/35-7/35
=8/35
b: =>5/7:x=4/3
=>x=5/7:4/3=5/7*3/4=15/28
c: =>x-1/3=15/8:4/5=15/8*5/4=75/32
=>x=75/32+1/3=257/96
d: =>2x+1/8=2/7
=>2x=9/56
=>x=9/112
e: =>2x=10/3-5/4-3/4=10/3-2=4/3
=>x=2/3
C
27 tháng 2 2023
\(a,\dfrac{2}{5}+\dfrac{3}{7}+\left(-\dfrac{3}{5}\right)\\ =\dfrac{2}{5}+\dfrac{3}{7}-\dfrac{3}{5}\\=\left(\dfrac{2}{5}-\dfrac{3}{5}\right)+\dfrac{3}{7}\\ =-\dfrac{1}{5}+\dfrac{3}{7}\\ =-\dfrac{7}{35}+\dfrac{15}{35}\\ =\dfrac{8}{35}\\ b,1-\dfrac{5}{7}:x=-\dfrac{1}{3}\\ =>\dfrac{5}{7}:x=1-\left(-\dfrac{1}{3}\right)\\ =>\dfrac{5}{7}:x=1+\dfrac{1}{3}\\ =>\dfrac{5}{7}:x=\dfrac{3}{3}+\dfrac{1}{3}\\ =>\dfrac{5}{7}:x=\dfrac{4}{3}\\ =>x=\dfrac{5}{7}:\dfrac{4}{3}\\ =>x=\dfrac{5}{7}.\dfrac{3}{4}\\ =>x=\dfrac{15}{28}\\ c,\dfrac{4}{5}\left(x-\dfrac{1}{3}\right)=\dfrac{15}{8}\\ =>x-\dfrac{1}{3}=\dfrac{15}{8}:\dfrac{4}{5}\\ =>x-\dfrac{1}{3}=\dfrac{15}{8}.\dfrac{5}{4}\\ =>x-\dfrac{1}{3}=\dfrac{75}{32}\\ =>x=\dfrac{75}{32}+\dfrac{1}{3}\\ =>x=\dfrac{257}{96}\)
\(d,\dfrac{2}{3}:\left(2x+\dfrac{1}{8}\right)=\dfrac{7}{3}\\ =>2x+\dfrac{1}{8}=\dfrac{2}{3}:\dfrac{7}{3}\\ =>2x+\dfrac{1}{8}=\dfrac{2}{3}.\dfrac{3}{7}\\ =>2x+\dfrac{1}{8}=\dfrac{2}{7}\\ =>2x=\dfrac{2}{7}-\dfrac{1}{8}\\ =>2x=\dfrac{16}{56}-\dfrac{7}{56}\\ =>2x=\dfrac{9}{56}\\ =>x=\dfrac{9}{56}:2\\ =>x=\dfrac{9}{112}\\ e,2x+\dfrac{3}{4}=\dfrac{10}{3}-\dfrac{5}{4}\\ =>e,2x+\dfrac{3}{4}=\dfrac{40}{12}-\dfrac{15}{12}\\ =>2x+\dfrac{3}{4}=\dfrac{25}{12}\\ =>2x=\dfrac{25}{12}-\dfrac{3}{4}\\ =>2x=\dfrac{25}{12}-\dfrac{9}{12}\\ =>2x=\dfrac{16}{12}\\ =>2x=\dfrac{4}{3}\\ =>x=\dfrac{4}{3}:2\\ =>x=\dfrac{4}{6}\\ =>x=\dfrac{2}{3}\)
2 tháng 8 2023
1: =>3^x=81
=>x=4
2: =>2^x=8
=>x=3
3: =>x^3=2^3
=>x=2
4: =>x^20-x=0
=>x(x^19-1)=0
=>x=0 hoặc x=1
5: =>2^x=32
=>x=5
6: =>(2x+1)^3=9^3
=>2x+1=9
=>2x=8
=>x=4
7: =>x^3=115
=>\(x=\sqrt[3]{115}\)
8: =>(2x-15)^5-(2x-15)^3=0
=>(2x-15)^3*[(2x-15)^2-1]=0
=>2x-15=0 hoặc (2x-15)^2-1=0
=>2x-15=0 hoặc 2x-15=1 hoặc 2x-15=-1
=>x=15/2 hoặc x=8 hoặc x=7
VN
Võ Ngọc Phương
CTVHS
VIP
2 tháng 8 2023
1. Tìm số tự nhiên x biết:
1) \(3^x.3=243\)
\(3^x=243:3\)
\(3^x=81\)
\(3^x=3^4\)
\(\Rightarrow x=4\)
_____
2) \(7.2^x=56\)
\(2^x=56:7\)
\(2^x=8\)
\(2^x=2^3\)
\(\Rightarrow x=3\)
_____
3) \(x^3=8\)
\(x^3=2^3\)
\(\Rightarrow x=3\)
_____
4) \(x^{20}=x\)
\(x^{20}-x=0\)
\(x\left(x^{19}-1\right)=0\)
\(\Rightarrow x=0\) hoặc \(x=1\)
5) \(2^x-15=17\)
\(2^x=17+15\)
\(2^x=32\)
\(2^x=2^5\)
\(\Rightarrow x=5\)
_____
6) \(\left(2x+1\right)^3=9.81\)
\(\left(2x+1\right)^3=729=9^3\)
\(\rightarrow2x+1=9\)
\(2x=9-1\)
\(2x=8\)
\(x=8:2\)
\(\Rightarrow x=4\)
_____
7) \(x^6:x^3=125\)
\(x^3=125\)
\(x^3=5^3\)
\(\Rightarrow x=5\)
_____
8) \(\left(2x-15\right)^5=\left(2x-15\right)^3\)
\(\rightarrow\left(2x-15\right)^5-\left(2x-15\right)^3=0\)
\(\left(2x-15\right)^3.\left[\left(2x-15\right)^2-1\right]=0\)
\(\Leftrightarrow\left\{{}\begin{matrix}\left(2x-15\right)^3=0\\\left(2x-15\right)^2-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{15}{2}\\x=7\\x=8\end{matrix}\right.\)
_____
9) \(3^{x+2}-5.3^x=36\)
\(3^x.\left(3^2-5\right)=36\)
\(3^x.\left(9-5\right)=36\)
\(3^x.4=36\)
\(3^x=36:4\)
\(3^x=9\)
\(3^x=3^2\)
\(\Rightarrow x=2\)
_____
10) \(7.4^{x-1}+4^{x+1}=23\)
\(\rightarrow7.4^{x-1}+4^{x-1}.4^2=23\)
\(4^{x-1}.\left(7+4^2\right)=23\)
\(4^{x-1}.\left(7+16\right)=23\)
\(4^{x-1}.23=23\)
\(4^{x-1}=23:23\)
\(4^{x-1}=1\)
\(4^{x-1}=4^1\)
\(\rightarrow x-1=0\)
\(x=0+1\)
\(\Rightarrow x=1\)
Chúc bạn học tốt
L
19 tháng 5 2022
a) (2x - 3)(6 - 2x) = 0
=> \(\left[{}\begin{matrix}2x-3=0\\6-2x=0\end{matrix}\right.=>\left[{}\begin{matrix}2x=3\\2x=6\end{matrix}\right.=>\left[{}\begin{matrix}x=\dfrac{3}{2}\\x=3\end{matrix}\right.\)
b) \(5\dfrac{4}{7}:x=13=>\dfrac{39}{7}:x=13=>x=\dfrac{39}{7}:13=>x=\dfrac{3}{7}\)
c) \(2x-\dfrac{3}{7}=6\dfrac{2}{7}=>2x-\dfrac{3}{7}=\dfrac{44}{7}=>2x=\dfrac{47}{7}=>x=\dfrac{47}{14}\)
d) \(\dfrac{x}{5}+\dfrac{1}{2}=\dfrac{6}{10}=>\dfrac{x}{5}=\dfrac{6}{10}-\dfrac{1}{2}=>\dfrac{x}{5}=\dfrac{1}{10}=>x.10=5=>x=\dfrac{1}{2}\)
e) \(\dfrac{x+3}{15}=\dfrac{1}{3}=>\left(x+3\right).3=15=>x+3=5=>x=2\)
21 tháng 12 2019
1) 3x+4 = 243
3x+4 = 35
=> x + 4 = 5
x = 5 - 4
x = 1
Vậy x = 1
2) (x-3)2 = 25
(x-3)2 = 52
=> x - 3 = 5
x = 5 + 3
x = 8
Vậy x = 8
3) (2x-1)3 = 125
(2x-1)3 = 53
=> 2x - 1 =5
2x = 5 + 1
2x = 6
x = 6:2
x = 3
Vậy x=3
5) 15 - x = 7 - (-2)
15 - x = 7 + 2
15 - x = 9
x = 15 - 9
x = 6
6) / x - 3 / = 7 - (-2)
/ x - 3 / = 7 + 2
/ x - 3 / = 9
TH1: x - 3 = 9
x = 9 + 3
x = 12
TH2: x - 3 = -9
x = -9 + 3
x = -6
Vậy x = 12,-6
7) /x-5/ = /-7/
x - 5 = -7
x = -7 + 5
x = -2
2 tháng 10 2020
Sorry mình nhầm câu a
a) (2x - 1)2 + (x + 3)2 - 5(x + 7)(x - 7) = 0
b) (x + 2)(x2 - 2x + 4) - x(x2 + 2) = 15
c) (x + 3)3 - x(3x + 1)2 + (2x - 1)(4x2 - 2x + 1) = 28
d) (x2 - 1)3 - (x4 + x2 + 1)(x2 - 1) = 0
Giải:
a) (2x - 1)2 + (x + 3)2 - 5(x + 7)(x - 7) = 0
\(\Leftrightarrow\) 4x2 - 4x + 1 + x2 + 6x + 9 - 5(x2 - 49) = 0
\(\Leftrightarrow\) 4x2 - 4x + 1 + x2 + 6x + 9 - 5x2 + 245 = 0
\(\Leftrightarrow\) 2x + 255 = 0
\(\Leftrightarrow\) 2x = - 255
\(\Leftrightarrow\) x = - 255 : 2
\(\Leftrightarrow\) x = \(-\frac{255}{2}\)
Vậy x = \(-\frac{255}{2}\)
b) (x + 2)(x2 - 2x + 4) - x(x2 + 2) = 15
\(\Leftrightarrow\) x3 + 8 - x3 - 2x = 15
\(\Leftrightarrow\) 8 - 2x = 15
\(\Leftrightarrow\) 2x = 8 - 1
\(\Leftrightarrow\) 2x = - 7
\(\Leftrightarrow\) x = - 7 : 2
\(\Leftrightarrow\) x = \(-\frac{7}{2}\)
Vậy x = \(-\frac{7}{2}\)
c) (x + 3)3 - x(3x + 1)2 + (2x - 1)(4x2 - 2x + 1) = 28
\(\Leftrightarrow\) x3 + 6x2 + 27x + 27 - x(9x2 + 6x + 1) + 8x3 - 1 = 28
\(\Leftrightarrow\) x3 + 6x2 + 27x + 27 - 9x3 - 6x2 - x + 8x3 - 1 = 28
\(\Leftrightarrow\) 26x + 26 = 28
\(\Leftrightarrow\) 26x = 28 - 26
\(\Leftrightarrow\) 26x = 2
\(\Leftrightarrow\) x = 2 : 26
\(\Leftrightarrow\) x = \(\frac{1}{13}\)
Vậy x = \(\frac{1}{13}\)
d) (x2 - 1)3 - (x4 + x2 + 1)(x2 - 1) = 0
\(\Leftrightarrow\) x6 - 2x2 + 1 - (x6 - 1) = 0
\(\Leftrightarrow\) x6 - 2x2 + 1 - x6 + 1 = 0
\(\Leftrightarrow\) -2x2 + 2 = 0
\(\Leftrightarrow\) -2x2 = - 2
\(\Leftrightarrow\) x2 = - 2 : (- 2)
\(\Leftrightarrow\) x2 = 1
\(\Leftrightarrow\) x = 1 hoặc x = - 1
Vậy x \(\in\) {1; - 1}
HH
7 tháng 8 2017
a)
<=> 10x - 35 + 16x - 10 = 5
<=> 10x + 16x = 5 + 35 + 10
<=> 26x = 50
<=> x = 50/26 = 25/13
-2.(x+3)-15=3.(4+2x)+7
-2x - 6 - 16 = 12 + 6x + 7
-2x - 6x = 12 + 7 + 6 + 16
-8x = 41
x = -5,125
\(-2.\left(x+3\right)-15=3.\left(4+2x\right)+7\)
\(-2x-6-15=12+6x+7\)
\(-2x-6x=12+7+6+15\)
\(-8x=40\Leftrightarrow x=-5\)
Vậy...
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