I) In case of the equation holds and it is for any . Hence either for any or for any , which proves b) and b'). II) In case of one obtains and the equation has exactly one solution . Hence: , which proves c).
i) in cAse of tHE EQuaTion holDs And IT Is For aNY . HEnce eItheR foR aNy or for Any , whicH proVEs b) anD b'). ii) in caSe oF onE obTAins and ThE equation haS exactly oNe sOlUtioN . Hence: , which ProveS C).