Does there exist a function f(x) defined for all x∈R and for all x,y∈R satisfying the inequality |f(x+y)+sinx+siny|<2?
The quadratic trinomials f(x) and g(x) are such that f′(x)g′(x)≥|f(x)|+|g(x)| for all real x. Prove that the product f(x)g(x) is equal to the square of some trinomial.
Solve the inequality: |x+2000|<|x−2001|.
Prove that |x|≥x. It may be helpful to compare each of |3|, |−4.3| and |0| with 3, −4.3 and 0 respectively.