Question
Find the range of $$f\left( x \right) = \operatorname{sgn} \left( {{x^2} - 2x + 3} \right)$$
A.
$$\left\{ {1,\, - 1} \right\}$$
B.
$$\left\{ 1 \right\}$$
C.
$$\left\{ { - 1} \right\}$$
D.
none of these
Answer :
$$\left\{ 1 \right\}$$
Solution :
$$\eqalign{
& {x^2} - 2x + 3 = {\left( {x - 1} \right)^2} + 1 > 0\,\forall \,x\, \in \,R \cr
& {\text{or }}f\left( x \right) = \operatorname{sgn} \left( {{x^2} - 2x + 3} \right) = 1 \cr
& {\text{Hence, the range is }}\left\{ 1 \right\} \cr} $$