Đặt 2005 là a-2
=>2007=a
2011 là a+2
2014 là a+4
Ta có
\(\left(a-2\right)a\left(a+2\right)\left(a+4\right)+16=\left(\left(a-2\right).\left(a+4\right)\right).\left(a\left(a+2\right)\right)+16\)
\(=\left(a^2+2a-8\right)\left(a^2+2a\right)+16\)
Đặt a^2+2a-4=k
Ta có
\(\left(k-4\right)\left(k+4\right)+16=k^2-16+16=k^2\)là số chính phương
Tick nha
chung minh tong abc+bca+cab khiong phai la so chinh phuong
Chung minh rang neu n la mot stn lon hon 1 thi so 2^n-1 khong the la so chinh phuong
chung minh rang: N=444...44 888...8 9(nchu so 4)( n-1 chu so 8) la so chinh phuong
Cho: A,B trong do Agom 2m chu so 1 , B gom m chu so 4
Chung minh rang A+B+C+1 la so chinh phuong
biet a+1 va 2a+1 (a thuoc N) dong thoi la 2 so chinh phuong. chung minh rang a chia het cho 24
chung to 2^2004+1 la so chinh phuong
cho 1 so chinh phuong co 4 chu so. Biet rang chu so tan cung cua no la so nguyen to, tong cac chu so cua no cung la so chinh phuong va can bac 2 cua no co tong cac chu so cung la so chinh phuong
cho a, b, c, d. chung minh rang a,ad, cd, abcd la so chinh phuong
cho S = abc +bca + cab .chung minh rang S khong phai la so chinh phuong
