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Ta có: A = 2 + 22 + 23 + ... + 22008
=> 2A = 22 + 23 + ... + 22009
=> 2A - A = 22009 - 2
=> A = 22009 - 2
Vậy A = 22009 - 2
=> 2A = 2.(22009 - 2)
=> 2A = 22010 - 4
=> 2A + 4 = 22010 - 4 + 4
=> 2A + 4 = 22010
=> 3x = 2010
Sai đề
\(A=2+2^2+2^3+...+2^{2008}\)
\(2A=2^2+2^3+2^4+...+2^{2009}\)
\(2A-A=\left(2^2+2^3+2^4+...+2^{2009}\right)-\left(2+2^2+2^3+...+2^{2008}\right)\)
\(A=2^{2009}-2\)
\(\Rightarrow2.\left(2^{2009}-2\right)+4=2^{3x}\)
\(\Rightarrow2^{2010}-4+4=2^{3x}\)
\(\Rightarrow2^{2010}=2^{3x}\)
=> 3x = 2010
=> x =670
![](https://rs.olm.vn/images/avt/0.png?1311)
a/ (x-3)(2y+1) = 7
=> 7 chia hết cho x-3
=> x-3=1;7;-1 hoặc -7
Kẻ bảng ra xong rồi tính x-3 thì tính x, tính được 2y+1 thì tìm y
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có : |x + 5| - (x + 5) = 0
<=> |x + 5| = (x + 5)
<=> x + 5 = x + 5 ( x bằng bất kì)
-x + 5 = x + 5
<=> -x - x = 5 - 5
=> -2x = 0
=> x = 0
ai có thể trả lời cho mình phần b ko rồi mình sẽ k
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 1:
\(\frac{4}{12}+\frac{4}{20}+\frac{4}{30}+...+\frac{4}{306}\)
\(=4\cdot\left(\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+...+\frac{1}{306}\right)\)
\(=4\cdot\left(\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+\frac{1}{5\cdot6}+...+\frac{1}{17\cdot18}\right)\)
\(=4\cdot\left(\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{17}-\frac{1}{18}\right)\)
\(=4\cdot\left(\frac{1}{3}-\frac{1}{18}\right)\)
\(=4\cdot\left(\frac{6}{18}-\frac{1}{18}\right)\)
\(=4\cdot\frac{5}{18}\)
\(=\frac{10}{9}\)
Bài 2 :
\(\left(3x-4\right)-\left(6x+7\right)=8\)
\(3x-4-6x-7=8\)
\(\left(3x-6x\right)-\left(4+7\right)=8\)
\(-3x-11=8\)
\(-3x=8+11\)
\(-3x=19\)
\(x=19:\left(-3\right)\)
\(x=\frac{-19}{3}\)
Vậy \(x=\frac{-19}{3}\)
b ) \(\left(\frac{4}{5}x+3\right):\left(-4\right)=\frac{1}{2}\)
\(\frac{4}{5}x+3=\frac{1}{2}\cdot\left(-4\right)\)
\(\frac{4}{5}x+3=-2\)
\(\frac{4}{5}x=\left(-2\right)-3\)
\(\frac{4}{5}x=-5\)
\(x=\left(-5\right):\frac{4}{5}\)
\(x=\left(-5\right)\cdot\frac{4}{5}\)
\(x=-4\)
Vậy \(x=-4\)
k nha !
\(\frac{4}{12}\)+\(\frac{4}{20}\)+...+\(\frac{4}{306}\)=\(\frac{4}{3.4}\)+\(\frac{4}{4.5}\)+...+\(\frac{4}{17.18}\)=4(\(\frac{1}{3}\)-\(\frac{1}{4}\)+\(\frac{1}{4}\)-\(\frac{1}{5}\)+...+\(\frac{1}{17}\)-\(\frac{1}{18}\))
=4(\(\frac{1}{3}\)-\(\frac{1}{8}\))=4.\(\frac{5}{24}\)=\(\frac{5}{6}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a.x^5=32=2^5\Rightarrow x=5\)
\(b.9^x=81=3^4\Rightarrow x=4\)
\(c.x^4=16=2^4\Rightarrow x=4\)
T ủng hộ mk nha ^...^ thank you
a, x5 = 32
x5 = 25
Vậy x = 2
b, 9x = 81
9x = 92
Vậy x = 2
c, x4 = 16
x4 = 24
Vậy x = 2
![](https://rs.olm.vn/images/avt/0.png?1311)
Bạn ơi, cái ý thứ 2 hình như đáp án là 6 thì phải, còn cách thình bày mình yếu lắm,đừng hỏi
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có :
\(\frac{3}{10}+\frac{3}{11}+\frac{3}{12}+\frac{3}{13}+\frac{3}{14}< \frac{3}{10}+\frac{3}{10}+\frac{3}{10}+\frac{3}{10}+\frac{3}{10}\)
\(\Rightarrow S< \frac{3}{10}.5\)
\(\Rightarrow S< 1,5\left(1\right)\)
Lại có :
\(\frac{3}{10}+\frac{3}{11}+\frac{3}{12}+\frac{3}{13}+\frac{3}{14}>\frac{3}{15}+\frac{3}{15}+\frac{3}{15}+\frac{3}{15}+\frac{3}{15}\)
\(\Rightarrow S>\frac{3}{15}.5\)
\(\Rightarrow S>1\left(2\right)\)
Từ ( 1 ) ; ( 2 )
\(\Rightarrow1< S< 1,5\)
\(\Rightarrow S\)ko phải là STN
a) (2-x-16)3=1000
=> 2-x-16 = 10
2-x = 10+16
2-x = 26
x = 2-26
x = -24
(x+1)5=1
=> x+1=1
x = 1-1
x = 0
c) 3x.3x+1=319
<=> 32x+1 = 319
=> 2x+1 = 19
2x = 19-1
2x = 18
x = 18:2
x = 9
d) 13x+32=33
13x = 33-32
13x = 1
=> x = 0
e) 22x-4=1024
=> 22x-4 = 210
<=> 2x-4 = 10
2x = 10+4
2x = 14
x = 14:2
x = 7
a.(x-14)^3=1000
(x-14)^3=10^3
=x-14=10
x=24
b,(x+1)^5=1
(x+1)^=1^5
x+1=1
x=0
c,3^x+3^x+1=3^19
=3^x+2=3^19
=x+2=19
x=17
d,13^x+32=33
13^x=1
x=0
e,2^2x-4=1024
2^2x-4=2^10
2x-4=10
2x=6
x=3