1 tìm x,y,z biết \(\dfrac{y+z+1}{x}\) = \(\dfrac{x+z+2}{y}\)=\(\dfrac{x+y-3}{z}\)=\(\dfrac{1}{x+y+z}\)
2 cho x..y.z=2 và x+y+z=0 tính giá trị biểu thức b=(x+y).(y+z).(x+z)
3 chmr
\(\dfrac{3}{1^2.2^2}\)+ \(\dfrac{5}{2^2.3^2}\)+\(\dfrac{7}{3^2.4^2}\)+ .............+\(\dfrac{4019}{2009^2.2010^2}\)< 1
4 cho \(\dfrac{x}{y+z+t}\)=\(\dfrac{y}{z+t+z}\)=\(\dfrac{z}{t+x+y}\)=\(\dfrac{t}{x+y+z}\)
tính giá trị biểu thức M =\(\dfrac{x+y}{z+t}\)+\(\dfrac{y+z}{t+x}\)+\(\dfrac{z+t}{x+y}\)+\(\dfrac{t+x}{z+y}\)
