S bang 2 mu 2 cong 4 mu 2 cong 6 mu 2 cong.......cong 20 mu 2
chứng minh ý a 8mu10 cong 2 mũ 20 chia hết cho41
chứng minh ý b 31 mu36 nhận 36 -313 mu 5 nhận 299 chia hết ch
chung minhý c 3 mu n công 3 cộng 2 mu n công 3 công 2 mu n công 2 công 2 mu n công 2 chia hết 6
chung minh y d d=2 cong 2 mu 2 cong 2mu 3 cong 2 mu 4 cong 2 mu 5 cong 2 mu 6 cong ....cong 2 mu 58 cong 2 mu 59 cong 2 mu 60 chia het cho 31
chung minh y e, e= 1cong 3 cong 3 mu 2 cong 3 mu 3 cong..cong 3 mu 98 cong 3 mu 99 chung minh e chia het cho5 chia het cho11
tong S =3 mu 0 cong 3mu 2cong 3mu 4 cong 3 mu 6 cong 3 mu 8 cong .......... cong 3 mu 2006 cong 3 mu 2008 tan cung bang chu so nao . vi sao
chung to rang B = 1/2mu 2 cong 1/3 mu 2 cong 1/4 mu 2 cong 1/5 mu 2 cong 1/6 mu 2cong 1/7 mu 2 cong 1/8 mu2 nho hon 1
Ta có :\(n^2-n=n.\left(n-1\right)\)
\(\implies\) \(n^2=\left(n-1\right)n+n\)
Áp dụng : với n=2017 thay vào ta có:
\(S=1+1.2+2+2.3+3+...+99.100+100\)
\(S=\left(1.2+2.3+...+99.100\right)+\left(1+2+...+100\right)\)
\(S=\frac{99.100.101}{3}+\frac{101.100}{2}\)
\(S=100.101.\left(\frac{99}{3}+\frac{1}{2}\right)\)
\(S=\frac{100.101.201}{6}\)
2 mu m cong 2 mu n bang 2 mu m cong n tim m va n
Chung to 4 cong 4 mu 2 cong 4 mu ba +...+ 4 mu 100 chia het cho 20
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tim x y thuoc z biet x mu 2 cong y nhan x cong y mu 2 bang x mu hai nhan y mu hai
cmr A=1 cong 5 cong 5 mu 2 cong 5 mu 3 cong ....cong 5 mu 21 chia het cho 6
5 mu n nhan 5 mu n cong 1 nhan 5 mu n cong 2 be hon hoac bang 10 mu 18