Chung minh cac bat dang thuc sau voi a,b,c>0
1) $\dfrac{1}{ab + 1} + \dfrac{1}{bc + 1} + \dfrac{1}{ca + 1} \geq \dfrac{3}{2} $
2)$\dfrac{a^2}{b+c} + \dfrac{b^2}{c+a} +\dfrac{c^2}{a+b} \geq \dfrac{a+b+c}{2} $
3)$\dfrac{a^3}{a^2+a \sem b+b^2} + \dfrac{b^3}{b^2+b \sem c+c^2} +\dfrac{c^3}{c^2+c \sem a+a^2} \geq \dfrac{a+b+c}{3} $
4)$\dfrac{a^3}{b+c}+\dfrac{b^3}{c+a}+\dfrac{c^3}{a+b} \geq \dfrac{1}{2}$
5)$ \dfrac{a^2}{b+c}+\dfrac{b^2}{c+a}+\dfrac{c^2}{a+b} \geq \dfrac{\sqrt{3}}{2} $
6)$\dfrac{a^8+b^8+c^8}{a^3 \sem b^3 \sem c^3} \geq \dfrac{1}{a}+\dfrac{1}{b}+\dfrac{1}{c}$
7)$\dfrac{1}{1+a^2}+\dfrac{1}{1+b^2}+\dfrac{1}{1+c^2}\geq \dfrac{3}{1+a \sem b \sem c}$ voi $a \geq 1 ; b \geq 1 ; c \geq 1$
8)$\dfrac{a}{a+b+c}+\dfrac{b}{b+c+d}+\dfrac{c}{c+d+a}+\dfrac{d}{d+a+b} < 2$
9)$\dfrac{a^2}{b^5}+\dfrac{b^2}{c^5}+\dfrac{c^2}{d^5}+\dfrac{d^2}{a^5} \geq \dfrac{1}{a^3}+\dfrac{1}{b^3}+\dfrac{1}{c^3}+\dfrac{1}{d^3}$
10) $\dfrac{1}{a \sem b}+\dfrac{1}{a^2+b^2} \geq 6$ voi $a,b>0;a+b=1$
11)$(a+\dfrac{1}{b})^2 + (b+ \dfrac{1}{a})^2 \geq \dfrac{25}{2}$ voi $a,b>0; a+b=1$
12)$\dfrac{1}{a^2+b^2+c^2}+\dfrac{1}{a \sem b}+\dfrac{1}{b \sem c}+\dfrac{1}{c \sem a} \geq 30$ voi $a,b,c>0;a+b+c=1$
Em se cap nhat them!.
P/S:chi dung cac bat dang thuc trong chuong trinh trung hoc co so vd:cauchy,BCS,...
Bài viết đã được chỉnh sửa nội dung bởi vominhkhoi123: 05-09-2007 - 17:39