chịu..................chịu..................chịu..............
chịu..................chịu..................chịu..............
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 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 S = abc +bca + cab .chung minh rang S khong phai 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
chung minh 2005.2007.2009.2011+16 la so chinh phuong
cho tam giac ABC.goi M La trung diem cua BC.Tren tia AM lay diem D sao cho M la trung diem cua doan thang AD .Noi B va C voi D?Tinh so do goc BA?Chung minh rang tam AMC= tam giac DMB?chung minh rang Ac//BD
CHO TAM GIAC ABC VUONG TAI A, DUONG CAO AH.TREN CANH BC LAY DIEM D SAO CHO BD=BA.DUONG VUONG GOC VOI BC TAI D CAT AC O E
A) SO SANH AE VA DE
B) CHUNG MINH TIA AD LA PHAN GIAC CUA GOC HAC
C) VE DK VUONG GOC VOIAC TAI K. CHUNG MINH RANG AK=AH
D) CHUNG MINH RANG AB+AC<BC+AH