1. 0<a<b<c<d<e (can also be equal) and a+b+c+d+e=1 proove that ad+dc+cb+be+ea<=0.2 2. f: Q -> Q , f(2)=2, x isn't equal to y. find f(x) which satisfy f((x+y)/(x-y))=(f(x)+f(y))/(f(x)-f(y)). 3. AM is the height of random ABC triangle. There have been chosen points N on AC and L on AB which satisfy angle NMA=angle LMA. proove that AM, BN, CL intersect on one point