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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) \(1+2-3-4+5+6-7-8+...+2001+2002-2003-2004\)
\(=\left(1+2-3-4\right)+\left(5+6-7-8\right)+...+\left(2001+2002-2003-2004\right)\)
\(=\left(-4\right)+\left(-4\right)+...+\left(-4\right)\)
\(=\left(-4\right)\cdot501=\left(-2004\right)\)
\(\left(7^{2003}+7^{2002}\right):7^{2001}\)
\(=\left(7^{2003}+7^{2002}\right).\frac{1}{7^{2001}}\)
\(=\frac{7^{2003}}{7^{2001}}+\frac{7^{2002}}{7^{2001}}\)
\(=7^2+7=49+7=56\)
( 72003 + 72002 ) \(\div\)( 72001 x 7 )
= ( 72003 + 72002 ) \(\div\)( 72001+1)
= ( 72003 + 72002 ) \(\div\)72002
= ( 72003 \(\div\) 72002 ) + ( 72002 \(\div\)72002)
= 72003-2002 + 72002-2002
= 71 + 70
= 7 + 1 = 8
HK TỐT
\(\left(7^{2003}.7^{2002}\right):\left(7^{2001}.7\right)\)
\(=\left(7^{2003}.7^{2002}\right):\left(7^{2001+1}\right)\)
\(=7^{2003}.7^{2002}:7^{2002}=7^{2003}.\left(7^{2002}:7^{2002}\right)\)
\(=7^{2003}.1=7^{2003}\)
\(\left(7^{2003}+7^{2002}\right):\left(7^{2001}.7\right)\)
\(=\left(7^{2003}+7^{2002}\right):7^{2002}\)
\(=7^{2003}:7^{2002}+7^{2002}:7^{2002}\)
\(=7^{2003}:7^{2002}+1\)
\(=7^{2002}.7:7^{2002}.1+1\)
\(=7^{2002}.\left(7-1\right)+1\)
\(=7^{2002}.6+1\)
Ta có: \(\left(7^{2003}+7^{2002}\right):\left(7^{2001}.7\right)\)
\(\Rightarrow\left(7^{2003}+7^{2002}\right):7^{2002}\)
\(\Rightarrow7^{2002}:7^{2003}+7^{2002}:7^{2002}\)
Tự tính tiếp nha
72003 chia het cho 72001
72002 chia het cho 72001
=> 72003 + 72002 chia het cho 7
=>
Ta có \(7^{2003}+7^{2002}\)
\(=7^{2001}.\left(7^2+7\right)\)
Ta thấy \(7^{2001}⋮7^{2001}\Rightarrow7^{2001}.\left(7^2+7\right)\)
Do đó \(7^{2003}+7^{2002}⋮7^{2001}\)
Vậy....