A=1+3+3^2+3^3+...+3^30
3A=3+3^2+3^3+3^4+...+3^31
3A-A=(3+3^2+3^3+3^4+...+3^31)-(1+3+3^2+3^3+...+3^30)
2A=3^31-1
A=(3^31-1)/2
=> A không phải là số chính phương
cho A=1+3+32+33+....+330 chung minh A k phai la so chinh phuong cho minh cach giai nha
cho A=3+4+42+...+420 chung minh rang A k phai la so chinh phuong
cho A=1+1919+93199+19931999 chung minh rang A k phai la so chinh phuong
cho a bang 2^2+2^3+...+2^20 chung minh rang A+4 khong phai la so chinh phuong
a) cho A = 1+3+5+7+...+(2n+1) Voi n thuoc N
chung to rang A la so chinh phuong
b)B=2+4+6+8+...+2n voi n thuocN
so B co phai la so chinh phuong ko
cho A=30+31+32+33+....+330 chung minh rang tong A ko phai la so chinh phuong
\(A=1+3^1+3^2+3^3+...+3^{30}\)
tim chu so tan cung cua A va chung minh rang A ko phai la so chinh phuong
Cho A= 10^2012 + 10^2011 + 10^2010 + 10^2009 + 8
a, chung minh A chia het cho 24
b, chung minh A ko phai la so chinh phuong
cho A =3+3^2+.........+3^2004
chung minh A chia het cho 130
A co phai la so chinh phuong hay khong
lam cu the nhe