Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
S\(=5+5^2+...+5^{2012}\)
=> S \(=(5+5^2+5^3+5^4)+(5^{2009}+5^{2010}+5^{2011}+5^{2012})\)
=> S = \((5+5^2+5^3+5^4)+...+5^{2008}\cdot(5+5^2+5^3+5^4)\)
=> S = \(780+...+5^{2008}\cdot780\)
=> S= \(780\cdot(1+...+5^{2008})\)
=> S=\(12.65.(1+...+5^{2008})⋮5(đpcm)\)
A=2+22+..............+22013
2A=22+23+.............+22014
2A-A={22+23+.....+22014} - {2+22+......+22013}
A=22014-2
Vì A=22014-2 và B=22014 nên a<b
Ta có: A=2+2^2+...+2^2013
=>2A=2^2+2^3+...+2^2014
=>2A-A=(2^2+2^3+...+2^2014)-(2+2^2+...+2^2013)
=>A=2^2014-2<B=2^2014
Vậy A<B
a)
\(\left(2x-1\right)^2-81=0\)
\(\Rightarrow\left(2x-1\right)^2=9\)
\(\Rightarrow\left[\begin{array}{nghiempt}2x-1=9\\2x-1=-9\end{array}\right.\)
\(\Rightarrow\left[\begin{array}{nghiempt}x=5\\x=-4\end{array}\right.\)
Vậy x=5 ; x = - 5
b)
\(3^{x+2}+3^{x+1}-3^x=297\)
\(\Rightarrow3^x\left(9+3-1\right)=297\)
\(\Rightarrow3^x.11=297\)
\(\Rightarrow3^x=27\)
=> x = 3
Vậy x = 3
c)
\(3^x+2.3^{x-1}=405\)
\(\Rightarrow3^{x-1}\left(3+2\right)=405\)
\(\Rightarrow3^{x-1}.5=405\)
\(\Rightarrow3^{x-1}=81\)
=> x - 1 = 4
=> x = 5
Vậy x = 5
a) ( 2x-1 ) 2 - 81 = 0
( 2x-1 ) 2 = 0 + 81
( 2x-1 ) 2 = 81
( 2x-1 ) 2 = 92
2x-1 = 9
2x= 9+1
2x = 10
x= 10:2
x=5
Vậy x=5.
a: \(\Leftrightarrow\left[\left(3x+14\right):4-3\right]:2=1\)
=>(3x+14):4-3=2
=>(3x+14):4=5
=>3x+14=20
=>3x=6
hay x=2
b: \(\Leftrightarrow\left[\left(x:4+17\right):10+3\cdot16\right]:10=5\)
\(\Leftrightarrow\left(x:4+17\right):10=50-48=2\)
=>x:4+17=20
=>x:4=3
hay x=12
c: \(\Leftrightarrow2\cdot15^2+\left[2\cdot125-\left(2x+4\right)\cdot5\right]:19=453\)
\(\Leftrightarrow250-\left(2x+4\right)\cdot5=\left(453-450\right)\cdot19=57\)
=>5(2x+4)=197
=>2x+4=197/5
=>2x=177/5
hay x=177/10
d: \(\Leftrightarrow\left(19x+50\right):14=5^2-4^2=9\)
=>19x+50=126
=>19x=76
hay x=4
e: \(\Leftrightarrow2\cdot3^x=10\cdot3^{12}+8\cdot3^{12}=18\cdot3^{12}\)
\(\Leftrightarrow3^x=3^2\cdot3^{12}=3^{14}\)
hay x=14
f: \(\Leftrightarrow3\left(x+2\right):7=30\)
=>3(x+2)=210
=>x+2=70
hay x=68
g: \(2480-1570+200-x+5=1010\)
=>1115-x=1010
hay x=105
:v thế là bn ko bt lm r