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\(\left(7^{2003}+7^{2002}\right):7^{2001}\)
\(=\left(7^{2003}+7^{2002}\right).\frac{1}{7^{2001}}\)
\(=\frac{7^{2003}}{7^{2001}}+\frac{7^{2002}}{7^{2001}}\)
\(=7^2+7=49+7=56\)
S = 1-2-3+4+5-6-7+8+...+2001-2002-2003+2004
S = (1-2-3+4) + (5-6-7+8) + ...+ (2001-2002-2003+2004)
S = 0 + 0 + ...+ 0
S = 0
a) Ta có: S = 1 - 2 - 3 + 4 + 5 - 6 - 7+ 8 + ... + 2001 - 2002 - 2003 + 2004
\(\Rightarrow\) S = (1 - 2 - 3 + 4) + (5 - 6 - 7+ 8) + ... + (2001 - 2002 - 2003 + 2004)
\(\Rightarrow\) S = (-4 + 4) + (-8 + 8) + ... + (-2004 + 2004)
\(\Rightarrow\) S = 0 + 0 + ... + 0
\(\Rightarrow\) S = 0
a) \(1-2-3+4+5-6-7+...+2001-2002-2003+2004\)
\(=\left(1-2-3+4\right)+\left(5-6-7+8\right)+...+\left(2001-2002-2003+2004\right)\)
\(=0+0+...+0=0\)
b) \(1+2-3-4+5+6-7-8+...+2001+2002-2003-2004\)
\(=\left(1+2-3-4\right)+\left(5+6-7-8\right)+...+\left(2001+2002-2003-2004\right)\)
\(=\left(-4\right)+\left(-4\right)+...+\left(-4\right)\)
\(=\left(-4\right)\cdot501=\left(-2004\right)\)
7^2005 + 7^2004 - 7^2003
= 7^2002 . 7^3 + 7^2002 . 7^2 - 7^2002 . 7^1
= 7^2002 . ( 7^3 + 7^2 - 7^1 ) chia hết cho 7^2002
Vậy 7^2005 + 7^2004 - 7^2003 chia hết cho 7^2002
Ta có:
\(\left(7^{2005}+7^{2004}-7^{2003}\right)\div7^{2002}\)
\(=\left(7^{2002}\cdot7^3+7^{2002}\cdot7^2-7^{2002}\cdot7\right)\div7^{2002}\)
\(=7^{2002}\left(7^3+7^2-7\right)\div7^{2002}\)
\(=7^3+7^2-7\)
\(=343+49-7\)
\(=385\)
\(\frac{7^{2003}+7^{2002}}{7^{2001}}\)=\(\frac{7^{2003}}{7^{2001}}+\frac{7^{2002}}{7^{2001}}\)=\(\frac{7^{2001}.7^2}{7^{2001}}+\frac{7^{2001}.7}{7^{2001}}\)= 72 + 7 = 56
(72003 + 72002) : 72002
= (72003 + 72002) . 1/72002
\(=\frac{7^{2003}}{7^{2002}}+\frac{7^{2002}}{7^{2002}}=7+1=8\)
= 7 ^ 2002 + 7 ^2003 ÷ 7 ^ 2002 +7 ^ 2002 = 7