acho tam giac abc vuong tai A duong cao AH cat duong phan giac bd tai I 

achung minh tam giac abh dong dang voi tam giac CBA

b chung minh ia.bh=ih.ba

c chung minh hi/la=ad/Dc

cho a,b,c thuoc z , chung minh rang : a(c-b) - b(-a-c) =c(a+b0

cho a/b=c/b chung minh rang a^2+c^2/b^2+c^2

cho a/b =b/c =c/d chinh minh rang ( a + b + c ) / (b+ c + d)  = a/d 

cho 2/a=1/b+1/c(a,b,c khac 0,a khac c).Chung minh rang b/c=b-a/a-c

1. Cho a,b la 2 so duong thoa a+b<=1.chung minh rang \(6b+\frac{1}{3a}+\frac{4}{b}\ge11\).

2. cho a,b,c la cac so nguyen duong sao cho (a-b).(a-c).(b-c)=a+b+c

a. chung minh rang a+b+c chia het cho 2

b. Tim gia tri nho nhat cua M=a+b+c

cho a/2013 = b/2014 = c/2015 . chung minh rang : 4(a - b)(b - c) = (c -a ) ^2

Cho a/(b+c)+b/(c+a)+c/(a+b)=1. chung minh rang

a^2/(b+c)+b^2/(c+a)+c^2/(a+b)=0

Cho 1/c=1/2(1/a+1/b)(với a,b,c khác 0;b khác c)chứng minh rang a/b=a-c/c-b