We have x=2[x2]+1. Hence, x=t, or x=t+21, where t is an integer.
If x=t, we have
[x2]−2x+1=[t2]−2t+1=t2−2t+1=(t−1)2=0⇔t=1⇔x=1.
If x=t+21, then
[x2]−2x+1=[(t+21)2]−2(t+21)+1=[t2+t+41]−2t−1+1.
Since t2+t+41 is not an integer, [t2+t+41]=t2+t.
So,
[x2]−2x+1=t2+t−2t−1+1=t2−t.
Thus,
t2−t=0⇔t=0 or t=1⇔x=21 or x=23.
Therefore, the solutions are x=1, x=21, and x=23.