已知二次函数f(x)=ax^2+x.若对任意x1,x2∈R有f[(x1+x2)/2]≤1/2[f(x1)+f(x2)]成立,不等式f(x)

Question

已知二次函数f(x)=ax^2+x.若对任意x1,x2∈R有f[(x1+x2)/2] ≤ 1/2[f(x1)+f(x2)]成立,不等式f(x)

Answer 1

f((x1+x2)/2)0
f(x)