Dat A =1+2+22+23+...+250
=> 2A=2+22+23+24+...+251
=> 2A-A= 2+22+23+24+...+250 - ( 1+2+22+23+...+250 )
=> A=251-1
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Dat A =1+2+22+23+...+250
=> 2A=2+22+23+24+...+251
=> 2A-A= 2+22+23+24+...+250 - ( 1+2+22+23+...+250 )
=> A=251-1
tinh S=1/2+1/2mu2+1/2mu3+...+1/2mu20
2+2mu2+...+2mu500
tinh rut gon
tinh S=1mu2+2mu2+.....+10mu2
cho bieu thuc A= 2+2mu2 + 2mu3 +.....+2mu40
chung to rang A chia het cho 3, 7
tinh tong A . tim so tu nhien x de A+2 = 2 mua x-1
Cho b=1+2+2mu2+2mu3+...+2mu6,A=2mu2+2mu3+2mu4+..+2mutam chứng minh rằng A=4B
\(S=\dfrac{2mu2}{1.2}+\dfrac{2mu2}{2.3}+\dfrac{2mu2}{3.4}+...+\dfrac{2mu2}{2022.2023}\)
(mu = mũ)
1\2+1\2mu2+1\2mu3+......+1\2mu100
cho s = 1+2+2mu2+...+2mu2018 tính s