13+23+....+1003
=(1+2+....+100)2
=50502 la SCP
13+23+....+1003
=(1+2+....+100)2
=50502 la SCP
cho S= 1*2*3 +2*3*4 +3*4*5+....+k*(k+1)*(k+2) . chung minh 4S=1 la so chinh phuong
chung minh A = n*(n+1)*(n+2)*(n+3)khong la so chinh phuong voi moi n la so tu nhien
tim tat ca cac so chinh phuong gom 4 chu so biet rang khi ta them 1 don vi vao chu so hang nghin them 3 dom vi vao hang tram them 5 don vi vao hang chuc them 3 don vi vao hang don vi ta van co 1 so chinh phuong
tim mot so chinh phuong co 4 chu so vua la so chinh vua la so lap phuong
444...488...89 co phai so chinh phuong ko?
n so 4; n-1so 8
giup minh voi
Tim so tu nhien n sao cho n^3-6n^2+9n-2 la so chinh phuong
cmr : tổng bình phương 2 số lẻ bất kì không phai la so chinh phuong
tim so tu nhien N co 2 chu so,biet rang 2N+1 va 3N+1 la cac so chinh phuong
cho a la 1 so chinh phuong co 4 chu so biet 2 chu so dau va 2 chu so cuoi cua giong nhau hoi a la bao nhieu