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\(7\left(x-9\right)=35\Leftrightarrow x-9=5\Leftrightarrow x=14\)
Câu 2: \(2^x=2^2\cdot2\Leftrightarrow2^x=2^3\Leftrightarrow x=3\)
Câu 3: \(2\cdot3^{x-1}=54\Leftrightarrow3^{x-1}=27\Leftrightarrow3^{x-1}=3^3\Leftrightarrow x-1=3\Leftrightarrow x=4\)
Câu 4: \(42-\left(2x+32\right)+12:2=6\)
\(\Leftrightarrow42-2x-32+6=6\)
\(\Leftrightarrow-2x=6-6+32-42=-10\)
\(\Leftrightarrow x=5\)
Cau 1: 7.(x-9)=35
x-9=35:7
x-9=5
x=5+9
x=14
Cau2: 2:2^x=2^2.2
2:2^x=8
2^x=8.2
2^x=16
=> x=4
c) 2x - 49 = 5 . 32
2x - 49 = 5 . 9
2x - 49 = 45
2x = 45 + 49
2x = 94
x = 94 : 2
x = 47
a)4^x=64
4^x=4^3
<=>x=3
b)3^x-1=27
3^x-1=3^3
<=>x-1=3
x=3+1
x=4
c)26+8x-6x=46
26+x(8-6)=46
26+2x=46
2x=46-26
2x=20
x=20:2
x=10
d)\(25\le5^x\le625\)
<=>\(5^2\le5^x\le5^4\)
<=>\(2\le x\le4\)
<=>\(x\in\left\{2;3;4\right\}\)
e)10+2x=4^5:4^3
10+2x=4^5-3
10+2x=4^2
10+2x=16
2x=16-10
2x=6
x=6:2
x=3
a) 4x = 64
\(\Rightarrow\)4x = 43
\(\Rightarrow\)x = 3
b) 3x - 1 = 27
\(\Rightarrow\)3x - 1 = 33
\(\Rightarrow\)x - 1 = 3
\(\Rightarrow\)x = 4
c) 26 + 8x - 6x = 46
\(\Rightarrow\)26 + 2x = 46
\(\Rightarrow\)2x = 46 - 26
\(\Rightarrow\)2x = 20
\(\Rightarrow\)x = 10
d) 25 \(\le\)5x \(\le\)625
\(\Rightarrow\)52\(\le\)5x\(\le\)54
\(\Rightarrow\)x \(\in\){ 2 ; 3 ; 4 }
e) 10 + 2x = 45 : 43
\(\Rightarrow\)10 + 2x = 42 = 16
\(\Rightarrow\)2x = 16 - 10
\(\Rightarrow\)2x = 6
\(\Rightarrow\)x = 3
Gọi tổng trên là A.Ta có
\(A=\frac{1}{15}+\frac{1}{35}+\frac{1}{63}+\frac{1}{99}+\frac{1}{143}+\frac{1}{195}\)
\(2A=\frac{2}{15}+\frac{2}{35}+\frac{2}{63}+\frac{2}{99}+\frac{2}{143}+\frac{2}{195}\)
\(2A=\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}+\frac{2}{11.13}+\frac{2}{13.15}\)
\(2A=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}\)
\(2A=\frac{1}{3}-\frac{1}{15}\)
\(2A=\frac{5}{15}-\frac{1}{15}\)
\(2A=\frac{4}{15}\)
\(A=\frac{4}{15}:2\)
\(A=\frac{2}{15}\)
a: =>|x-5|=5-7x+7x+28=33
=>x-5=33 hoặc x-5=-33
=>x=-28 hoặc x=38
b: 1<=x-1<=2
=>2<=x<=3
=>x=2 hoặc x=3
c: \(0< =x-5< =2\)
=>5<=x<=7
=>\(x\in\left\{5;6;7\right\}\)
d: -4<x+3<4
=>-7<x<1
=>\(x\in\left\{-6;-5;...;-1;0\right\}\)
e: |x|<=3
=>\(x\in\left\{-3;-2;-1;0;1;2;3\right\}\)
f: |x+1|<=3
=>-3<=x+1<=3
=>-4<=x<=2
=>\(x\in\left\{-4;-3;-2;-1;0;1;2\right\}\)
6)\(3.\left(x+1\right)-2^3.2=11\)
\(3\left(x+1\right)-2^4=11\)
\(3.\left(x+1\right)=11+16\)
3.(x+1)=27
x+1=27:3
x+1=9
x=9-1
x=8
Vậy x=8
7) \(180-2.\left(x+5\right)^2=130\)
\(2.\left(x+5\right)^2=180-130\)
2.(x+5)2=50
(x+5)2=50:2
(x+5)2=25
x+5=5 hoặc x+5=-5
x=5-5 x=-5-5
x=0 x=-10
Vậy x=0 hoặc x=-10