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1/a) 12 - x= 1-(-5)
12 - x = 6
x= 12-6
x=6
b)| x+4|= 12
x+4 = \(\pm\)12
*x+4=12
x=8
*x+4= -12
x=-16
2/Tìm n
\(n-5⋮n+2\)
=> \(n+2-7⋮n+2\)
mà \(n+2⋮n+2\)
=> 7\(⋮\)n+2
=> n+2 \(\varepsilon\)Ư(7)= {1;-1;7;-7}
| n+2 | 1 | -1 | 7 | -7 |
| n | -1 | -3 | 5 | -9 |
3/a)4.(-5)2 + 2.(-12)
= 2.2.(-5)2 + 2.(-12)
=2[2.25.(-12)]
=2.(-600)
=-1200
ta có:
\(\left(7\frac{1}{2}.8\frac{3}{70}+8\frac{3}{70}.\frac{9}{4}+\frac{19}{4}.8\frac{3}{70}+5\frac{1}{2}.8\frac{3}{70}\right):x=1126\)
\(8\frac{3}{70}\left(7\frac{1}{2}+\frac{9}{4}+\frac{19}{4}+5\frac{1}{2}\right):x=1126\)
\(\frac{563}{70}.\left(\frac{15}{2}+7+\frac{11}{2}\right):x=1126\)
\(\frac{563}{70}.20:x=1126\)
\(\frac{1126}{70}:x=1126\)
\(=>x=\frac{1126}{7}:1126\)
\(=>x=\frac{1}{7}\)
cho mình nha các bạn.
Ta có : \(n+4=n-1+\)\(5\)
Ta thấy : \(\left(n-1\right)⋮\left(n-1\right)\)
Nên \(\left(n+4\right)⋮\left(n-1\right)\Leftrightarrow5⋮\)\(\left(n-1\right)\)
\(\Leftrightarrow\left(n-1\right)\inƯ\left(5\right)=\)\((1;5)\)
| N - 1 | 1 | 5 |
| N | 2 | 6 |
a) \(n+4⋮n-1\Rightarrow\left(n-1\right)+5⋮n-1\Rightarrow5⋮n-1\Rightarrow n-1\inƯ\left(5\right)\)
\(\Rightarrow n-1\in\left\{1;5;-1;-5\right\}\Rightarrow n\in\left\{2;6;0;-4\right\}\)
b) \(n^2+2n-3=\left(n^2+n\right)+n-3=n\left(n+1\right)+n-3\)
vì \(n\left(n-1\right)⋮n-1\)\(\Rightarrow n-3⋮n+1\Rightarrow\left(n+1\right)-4⋮n-1\Rightarrow4⋮n-1\Rightarrow n-1\inƯ\left(4\right)\)
\(\Rightarrow n-1\in\left\{1;2;4;-1;-2;-4\right\}\)
\(\Rightarrow n\in\left\{2;3;5;0;-1;-3\right\}\)
a) (2n-1)4 : (2n-1) = 27
(2n-1)3 = 27 =33
=> 2n - 1= 3
=> 2n = 4
n = 2
phần b,c làm tương tự nha bn
d) (21+n) : 9 = 95:94
(2n+1) : 9 = 9
2n + 1 = 81
2n = 80
n = 40
Bài 1:
a, \(\left(x-2\right)^2=9\)
\(\Rightarrow x-2\in\left\{-3;3\right\}\Rightarrow x\in\left\{-1;5\right\}\)
b, \(\left(3x-1\right)^3=-8\)
\(\Rightarrow3x-1=-2\Rightarrow3x=-1\)
\(\Rightarrow x=-\dfrac{1}{3}\)
c, \(\left(x+\dfrac{1}{2}\right)^2=\dfrac{1}{16}\)
\(\Rightarrow x+\dfrac{1}{2}\in\left\{-\dfrac{1}{4};\dfrac{1}{4}\right\}\)
\(\Rightarrow x\in\left\{-\dfrac{3}{4};-\dfrac{1}{4}\right\}\)
d, \(\left(\dfrac{2}{3}\right)^x=\dfrac{4}{9}\)
\(\Rightarrow\left(\dfrac{2}{3}\right)^x=\left(\dfrac{2}{3}\right)^2\)
Vì \(\dfrac{2}{3}\ne\pm1;\dfrac{2}{3}\ne0\) nên \(x=2\)
e, \(\left(\dfrac{1}{2}\right)^{x-1}=\dfrac{1}{16}\)
\(\Rightarrow\left(\dfrac{1}{2}\right)^{x-1}=\left(\dfrac{1}{2}\right)^4\)
Vì \(\dfrac{1}{2}\ne\pm1;\dfrac{1}{2}\ne0\) nên \(x-1=4\Rightarrow x=5\)
f, \(\left(\dfrac{1}{2}\right)^{2x-1}=8\) \(\Rightarrow\left(\dfrac{1}{2}\right)^{2x-1}=\left(\dfrac{1}{2}\right)^{-3}\) Vì \(\dfrac{1}{2}\ne\pm1;\dfrac{1}{2}\ne0\) nên \(2x-1=-3\) \(\Rightarrow2x=-2\Rightarrow x=-1\) Chúc bạn học tốt!!!
35 - 3(x) = 5. (23-4)
35 - 3x = 5.(8-4)
35 - 3x = 5.4
35 - 3x = 20
3x = 35-20
3x = 15
x = 15 : 3
x = 5
35 - 3(x) = 5 (23 -4)
35 - 3x = 5.(8 - 4 )
35 - 3x = 5.4
35 - 3x = 20
3x = 35 - 20
3x = 15
x = 15 : 3
x = 3
Vậy x = 3