Cmr cac so la so chinh phuong
\(A=\)111...1555...56
n chu so 1,n-1 chu so 5
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)Cho A= 111...1555...56 ( n chu so 1 , n-1 chu so 5 ) . Cmr : A la so chinh phuong
CMR neu A=111...1(200 chu so 1) va B=222...2 (100 chu so 2) thi A-B la mot 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=111...12(n chu so 1);b=111...14(n chu so1)
Cmr:ab+1la so chinh phuong
Ta thấy b = a + 2
\(ab+1=a\left(a+2\right)+1=a^2+2a+1\)
\(=a^2+a+a+1=a\left(a+1\right)+\left(a+1\right)=\left(a+1\right)\left(a+1\right)=\left(a+1\right)^2\)
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tim mot so chinh phuong gom4 chu so abcd = k mu 2 sao cho chuso cuoi la snt so k co tong cac chu so la 1 so chinh phuong
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a, so co tong cac chu so la 2004 khong la so chinh phuong
b, so co tong cac chu so la 2006 khong la so chinh phuong
c, n = 20044+20043+20042+23 khong 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
neu a la so gam 200 chu so 1 va B la so gom 100 chu so 2 CMR A-B la so chinh phuong
Cho : A=111...1(2n chu so 1) - 888...8(n so 8)
Chung minh A la so chinh phuong.
Chieu mai nop roi . giup minh nha . Thanks.