Cho \(\dfrac{a}{b-c}+\dfrac{b}{c-a}+\dfrac{c}{a-b}=0\).CM \(\dfrac{a^2}{\left(b-c\right)^2}+\dfrac{b^2}{\left(c-a\right)^2}+\dfrac{c^2}{\left(a-b\right)^2}=0\)
Cho a + b + c + d = 0. Tính \(M=\left(1+\dfrac{a}{b}\right)\left(1+\dfrac{b}{c}\right)\left(1+\dfrac{c}{a}\right);N=\dfrac{1}{b^2+c^2-a^2}+\dfrac{1}{a^2+c^2-b^2}+\dfrac{1}{a^2+b^2-c^2}\)
Chứng minh rằng nếu:\(c^2+2\left(ab-ac-bc\right)=0\left(b\ne0;a+b\ne c\right)\)
thì:\(\dfrac{a^2+\left(a-c\right)^2}{b^2+\left(b-c\right)^2}=\dfrac{a-c}{b-c}\)
Cho \(\left|a\right|\ge\left|b\right|\), ta có: \(\dfrac{\left|a\right|}{2009+\left|a\right|}\ge\dfrac{\left|b\right|}{2009+\left|b\right|}\)
Chứng minh rằng: \(\dfrac{\left|x\right|}{2009+\left|x\right|}+\dfrac{\left|y\right|}{2009+\left|y\right|}\ge\dfrac{\left|x-y\right|}{2009+\left|x-y\right|}\)với các số x,y bất kỳ
Cho a-b+c=-4. Tính B = \(\dfrac{a^3-b^3+c^3+3abc}{\left(a+b\right)^2+\left(b+c\right)^2+\left(c-a\right)^2}\)
Cho \(\dfrac{a}{b+c}+\dfrac{b}{c+a}+\dfrac{c}{a+b}=1\)Chứng minh \(M=\dfrac{a^2}{b+c}+\dfrac{b^2}{c+a}+\dfrac{c^2}{a+b}=0\)
Cho a + b + c= 3
Tính A=\(\dfrac{a^3+b^3+c^3-3abc}{\left(a-b\right)^2+\left(b-c\right)^2+\left(c-a\right)^{ }2}\)
Cho a,b,c và x,y,z khác nhau và khác 0
CMR: \(\text{Nếu }\dfrac{a}{x}+\dfrac{b}{y}+\dfrac{c}{z}=0,\text{ }\text{ }\text{ }\text{ }\text{ }\text{ }\dfrac{x}{a}+\dfrac{y}{b}+\dfrac{z}{c}=1\)
\(\text{Thì }\dfrac{x^2}{a^2}+\dfrac{y^2}{b^2}+\dfrac{z^2}{c^2}=1\)
tìm các số a và b sao cho phân thức \(\dfrac{x^2+5}{x^3-3x-2}\)viết được thành \(\dfrac{a}{x-1}+\dfrac{b}{\left(x+1\right)^2}\)