cho S = abc +bca + cab .chung minh rang S khong phai la so chinh phuong
chung minh tong abc+bca+cab khiong phai la so chinh phuong
Cho a,b,c la cac chu so khac nhau va khac 0.Tim abc biet
a. abc=11.(a+b+c)
b. abc+bca+cab lamot so chinh phuong
c. abc+bca+cab=777
Cho n thuoc N va n-1 khong chia het cho 4
CMR : 7^n +2 khong la so chinh phuong
trên bảng viết 99 số :1,2,3,4,...,99. cu moi lan nguoi ta xoa di hai so bat ki , roi lai viet gia tri cua tong hai so vua xoa vao bang cuoi cung tren bang chi con lai mot so , gia su so do la k . hay tim k va chung to k khong phai la so chinh phuong
Cho A = 3+3^2 + 3^3+... +3^2016
a, Tinh A
b, Tim chu so tan cung cua A
c,A co la so chinh phuong khong
Chung minh rang neu n la mot stn lon hon 1 thi so 2^n-1 khong the la so chinh phuong
1 stn so 1c/s1 2c/s2 3c/s3 4c/s4 co the la so chinh phuong khong vi sao
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