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a, 7.213 và 216
ta có: 216 = 213. 23 = 213 .8
vì 7. 213 < 213 .8 nên 7.213 <216
a)
Ta có :
72^45 - 72^44 = 72^44 x 72 - 72^44 x 1 =72^44 x (72-1) = 72^44 x 71
72^44 - 72^43 = 72^43 x 72 - 72^43 x 1 =72^43 x (72-1) = 72^43 x 71
Vì 72^44>72^43 => 72^44 x 71 > 72^43 x 71 hay 72^45 - 72^44 > 72^44 - 72^43
b)
Ta có :
2500 = 25x100 = (25)100 = 32100
5200 = 52x100 = (52)100 = 25100
Vì 32 > 25 => 32100 > 25100 hay 2500 > 5200
1. Tim x
a. ( \(\frac{8}{27}\))x = ( \(\frac{2}{3}\))72
b. \(\frac{1}{3}\) . 3x = 7 . 32 . 92 - 2 . 3x
a. \(\left(\frac{8}{27}\right)^x=\left(\frac{2}{3}\right)^{72}\)
\(\left(\frac{2}{3}\right)^{3x}=\left(\frac{2}{3}\right)^{72}\)
\(\Rightarrow3x=72\Rightarrow x=24\)
Vậy x = 24
c) G = \(\frac{636363.37-373737.63}{1+2+3+...+2017}\)
G = \(\frac{63.10101.37-37.10101.63}{1+2+3+...+2017}\)
G = \(\frac{0}{1+2+3+...+2017}\)
=> G = 0
Vậy G = 0
a) \(E=\frac{1}{1.2.3}+\frac{1}{2.3.4}+...+\frac{1}{48.49.50}\)
\(\Rightarrow E=\frac{1}{2}\left(\frac{2}{1.2.3}+\frac{2}{2.3.4}+...+\frac{2}{48.49.50}\right)\)
\(\Rightarrow E=\frac{1}{2}\left(\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-\frac{1}{3.4}+...+\frac{1}{48.49}-\frac{1}{49.50}\right)\)
\(\Rightarrow E=\frac{1}{2}\left(\frac{1}{1.2}-\frac{1}{49.50}\right)\)
\(\Rightarrow E=\frac{1}{2}.\frac{612}{1225}\)
\(\Rightarrow E=\frac{306}{1225}\)
Vậy...
b) \(\frac{5.4^{15}.9^9-4.3^{20}.8^9}{5.2^9.6^{19}-7.2^{29}.27^6}=\frac{5.2^{30}.3^{18}-2^2.3^{20}.2^{27}}{5.2^9.2^{19}.3^{19}-7.2^{29}.3^{18}}=\frac{5.2^{30}.3^{18}-2^{29}.3^{20}}{5.2^{28}.3^{19}-7.2^{29}.3^{18}}\)
\(=\frac{2^{29}.3^{18}\left(5.2-3^2\right)}{2^{28}.3^{18}\left(5.3-7.2\right)}=\frac{2.1}{1}=2\)
d) Bạn xem lại đề nhé
b) A = 2009 . 2011
A = 2009 . ( 2010 + 1 )
A = 2009 . 2010 + 2009
B = 20102
B = 2010 . 2010
B = ( 2009 + 1 ) . 2010
B = 2009 . 2010 + 2010
Mà 2009 . 2010 + 2009 < 2009 . 2010 + 2010
Vậy A < B
d tương tự
c) 52n và 25n
52n = 25n
25n = 32n
Mà 25n < 32n
Vậy 52n < 25n
a) A = 20 + 21 + 22 + 23 + ............ + 22010
2A = 21 + 22 + 23 + 24 + .............. + 22011
2A - A = ( 21 + 22 + 23 + 24 + ............... + 22011 ) - ( 20 + 21 + 22 + 23 + ................ + 22010 )
A = 22011 - 1
Mà 22011 - 1 = 22011 - 1
Vậy A = B
\(B=3+3^2+3^3+.....+3^{2006}\)
\(\Rightarrow3B=3^2+3^3+....+3^{2007}\)
\(\Rightarrow2B=3^{2007}-3\)
\(\Rightarrow B=\frac{3^{2007}-3}{2}\)
\(2B+3=3^x\)
\(\Rightarrow2.\frac{3^{2007}-3}{2}+3=3^x\)
\(\Rightarrow3^{2007}-3+3=3^x\Rightarrow3^{2007}=3^x\Rightarrow x=2007\)
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